I think that there is an absorbant mat inside the belly pans that some of you are not aware of. The pan doesn't or shouldn't be a liquid containment on it's own. Also the diaper pictured above looks to have plastic buckles.

E. Williams 65 Coronet 500 3400lbs w/d, 446, Indy EZ'S, A&A transbrake,Comp 650 lift cam, 6.50 @ 105 mph 1/8th 10.25 @ 130mph 1/4