RussellR2D2's thread shows a great method to get the butt from Rick Flairing out. For the kidney, it would have been easier to heat bend it before gluing it in place but since that ship has sailed, get a big bucket from home depot and put some boiling water in it and submerge one side at a time. Get the bend you need and cool it in cold water. Another suggestion to keep it together is making the split rivets functional by putting the elastic in between the rivets on the kidney and ab. It'll be permanently attached like a clam shell but it'll hold straight and flush if done right. On the right side you can use snaps but in the center make a slot system to keep it aligned. Once again, gotta recommend RussellR2D2's build thread for that suggestion. One last suggestion, don't know if you plan on it or not but I would put some ABS paste on the outside and inside seems of your kidney shim. It'll make it stronger and the outside will look like it wasn't shimmed at all if done correctly. I will take some pics of mine tonight to show you what I mean if that doesn't make sense.