I-80_Standups

Ok so i bought a 905 cage a while back and it has been sitting for a while now and when i went to put it on yesterday i ran into a problem. Where it mounts to the bike furthest towards the rear (where the long mount bolt goes all the way through the frame and both sides of the cage) The bolt isnt long enough to go through all the way to get the nut on with the added width of the cage. Can someone please let me know what i am doing wrong? i know its something stupid but ithought i would ask here instead of waisting a half day trying to figure it out, thanks in advance