Check the file size of your common3.pac. It must not use more than 4.82 MB (5,053,855 bytes), considering that the PAC file itself is compressed.
Also, I think only certain items can be model swapped.
Hate to bring up an old topic, but I've had this same problem. My game got stuck at the strap loader when I replaced the Maxim Tomato with RandomTBush's "Sandvich." And, the file size of my common3.pac turned out to be 4.78 MB after the swap. That's pretty close to 4.82, but not quite. I guess that's too much anyway?