If the case just gets slightly rounded that is just normal expansion as these packs are built with 5.5mm cells and there is 4 cells for a total of 22mm and the case is 24.9mm this leaves 1.45mm for the case thickness. In high amp discharges on un assembled cell I noticed 0.2 to 0.3mm expansion per cell. This means you can get 1.2mm expansion which is enough to push out the case and make it not flat anymore.

I think in heavy cars/trucks using 3S or 4S is the way to go but I do understand some classes won't allow for anything more than 2S.

Your cut off is set properly so that is not creating any damage.

Never store the pack fully charged as this can damage it.