Shelling RotF Ravage

I recently bought a RotF Ravage with the express purpose of giving him more than a 'tuck my legs in and call it an alt-mode' Transformation. I have car model shells laying about, most of which are deluxe size. But now I've run into a problem
I've done kitbashing, and re-shelling, before... But all my previous re-shells had car alt-modes to start with. I used the places where the previous 'shell' attached to attach the new shell and would carefully use my dremel to cut the connection points from the previous shell and put it on the new shell and end up with new alt-modes for toys.
but With Ravage I'm running into trouble. I've got the right shell, he fits in under there just about right, I'll just need to add a joint to his hind legs to tuck them under a bit better, and I'm trying to figure out what to do with his hip guns.
I'm fairly certain I can figure out where to create the attachment points, and I'm sorting out where to cut the shell for the transformation, but what I've run into is that I don't know how to create a way to let the mold click together well after transforming.
I'm not sure that I have any of the toys to create the connection joints, does anyone know how to make them from scratch? I'm thinking maybe seeing if I have some peg/hole pieces or the like around, using those... anyone have any suggestions? This is by far the most extensive mod I've done so far.
I've done kitbashing, and re-shelling, before... But all my previous re-shells had car alt-modes to start with. I used the places where the previous 'shell' attached to attach the new shell and would carefully use my dremel to cut the connection points from the previous shell and put it on the new shell and end up with new alt-modes for toys.
but With Ravage I'm running into trouble. I've got the right shell, he fits in under there just about right, I'll just need to add a joint to his hind legs to tuck them under a bit better, and I'm trying to figure out what to do with his hip guns.
I'm fairly certain I can figure out where to create the attachment points, and I'm sorting out where to cut the shell for the transformation, but what I've run into is that I don't know how to create a way to let the mold click together well after transforming.
I'm not sure that I have any of the toys to create the connection joints, does anyone know how to make them from scratch? I'm thinking maybe seeing if I have some peg/hole pieces or the like around, using those... anyone have any suggestions? This is by far the most extensive mod I've done so far.