IPS #16 vs. IPS #3

[bigapple]

besides #3 having a less dense consistency, what exactly is the big difference and would one really have a much stronger bond than the other? i used #3 on my polycarbonate box and it seems to hold well but im thinking of upgrading to 3/8" thickness rather than 1/4 cuz mine leaks a tad and cracks around the holes that i drilled to put in some bolts, since the holes r too close to the edges... if im gunna upgrade in thickness, i was wondering if i should upgrade my solvent as well

thoughts or suggestions?

[hydrotinkerer]

The only difference is #16 is almost a gel like and seals irregular gaps, but sometimes as it dries it might develope small air bubbles. If your gaps are tight #3 or #4 is best. #4 is a little slower drying.