I had posted about achieving the texture of the football (using fondant covering) but I also wanted to ask for opinion...

My plan is to make the bottom half out of RK treats and the top out of cake.  My question is, will the bottom half make of RK hold up to the cake?   I think so, but any suggestions or thoughts are greatly appreciated!

When in doubt you can put some dowels into the RKT and a board under the cake part

Unless your cake is HUGE! it should hold up w/o a problem.  And what ropalma said stands :)