In order to avoid putting any clamping force on the snap itself,(debate on weather or not E6000 and metal snap and clamping can warp your ABS plastic), I came up with some clamping buddies.
1 1/2" square wooden blocks with 5/8" hole in center.
Just make sure the wooden block is thicker than the highest point of the snap and that the center hole is larger than the snap itself.
Put a small piece of duct tape over the back of the snap, apply glue and start clamping the nylon without putting any force on the metal snap.