I'm using your Simulator for about 2 weeks now and enjoying it a lot. Honestly i heard for faster simulators and they turned out not to be so and FastSim seems to be totally the most accurate and never failed me one single Recruit too much using Nusala so far, so i'm a big fan here. But...
But i think you could fix the side scrolling by sizing the horizontal frames using % and verticals as you wish since it shouldn't bother anyone.
Also i just saw refresh after refresh that you did a few nice and useful changes there on where we change and pick our troops. I would like to suggest making the box of the number of troops a big larger and the arrows a bit larger too and make sure they're as easy to click as possible without over-sizing them.
Another thing is i couldn't simulate hitting 2 camps in a row with one General. At least not with Nusala, didn't think of trying others but that would be very nice to be able to do that. Also try making those tabs of Generals a bit larger too so we can click them easier and quicker, just a bit. Camp's tabs could be a good example too, making them a bit higher as you use the full width too.
And one last thing. I would appreciate it if you'd make the click-zone on the picture on top-right where you click to pick the enemy camps as full sized as possible cause many times it doesn't catch my clicks unless i click right on center. Just a comfortability thing but i guessed these must be little things that could count as positive touches on the interface.
Also... Was thinking if you wanna touch the calculation structure maybe you could speed up a bit the usual brute power unit's simulations by limit-counting the meat-shield effect. Meaning, you can add an offense and deffense limit for each enemy camp for example which won't have to be calculated. Like, if you're using a Normal General let's say and planing to kill using a full wave of recruits or any other troops without splash or first strike skills you can be sure the max offense from player (supposing the player always has first hit in this scenarios and then enemy camp units) You can be sure the player's offense is no less than
"(Min Troop DMG) X Troop number. And that cuts the line then the same with the max and you may cut yourself some unnecessary calculations on
"Find Best Attack" simulations. Using this in double waves and trilples should be quite some difference considering you'll do better than this just attaching the loops you already been using.
Then again... I would like to hope you could get into some serious work in there and turn the simulations into something more intensely improved like, having calculations cut down a high % of different calculations that contain a very low minimal chance to win and don't pass a max % of win chance, then you can safely cut that out and repeat that for every X% of simulations with each troop and try to upgrade that efficiently by your hard work running tests and simulations to check for mistakes. That takes some time and some detailed work maybe but i think would be worth a lot if you try a quick mix for a test and see the results. (Of course you'd have to run a lot of tests of many kinds before you put it out but each success should help a lot if the numbers remain safe.)
On that note, you may as well add a "debugger-like" calculation in the end to check how reliable that simulation was and that can run on background real lightly and smooth as soon as the user is getting the fresh result of the simulation already. Mean time the reliability of the simulation can show as a % and a simple line easily visible on the bottom of the middle column with the note you wish and the result and also a button as an option to run the rest of the calculations from where it stopped. Which will be just extra time and simulations that been mostly considered from bad and worthless to even count already through the process anyway but if somebody wants to be extra sure or is playing risky hits and needs extra guarantees can get the full size there while everybody else will have it totally unnecessary in about 80% of the cases and most of those people won't find it even worth the time for such attacks that include double or triple waves of Recruits and Bowman that end with a safe cheap kill on final wave. In other words it should generally have absolutely no negative effect as long as you only play your numbers safe not cutting out possibly good combos and also as long as you make sure there's no bugs and it's all ready to go which should be pretty easy considering most of the processes should be just calling other functions and procedures you already have in use just like everything already runs perfectly fine and safe.
Also, offering people to log in and save the simulations they choose and find as the best and even give them the option to calculate the resources to be lost from minimum to maximum of each kind (Also the expected loses as simulator tells min and max expected troops to lose and picks the ones most likely to happen) in two different blocks of info about the final results of all their chosen simulations, which should allow people to keep track of their costs per each Adventure and even make it extremely much easier for people to come over there and drop a great guide that works on numbers for them and post it straight from your interfaces using your given tools and options and being able to share them through social medias too and of course on Forums here and so on. Have to say it does take a lot of work any of these starting from the first few lines i wrote the rest are no easy stuff to do i guess but hey, all i got is thoughts and ideas. :P I'm just the math guy with a million ideas.
Sorry for the long comment here just thought could be useful if you'd do them and hoping for the best since this is definitely the best simulator for me so far and haven't seen one to match your level at any point.
Wish you good luck and hoping for the best from the best and thanks for the simulator.