When gluing together dissimilar materials, what glue works best?

I must have cut and fitted 30 pieces of plastic the other day on the main gate and the bastion at the other end of the fortress. Crenellations each require 4 fitted pieces. Ugh. I’m making really efficient use of the plastic sheets but I wonder whether I’ll have enough Omni-Stick to finish the project. It's not made any more; I’ll have to find a replacement.

The fort is made of blue foam, 3/16" foamcore and hard plastic random stone pattern sheets. What kinds of glue will bind those materials?

Weld Bond white glue works well on foamcore, as does plain Elmer's. If you use a low temp hot glue gun, that can work as well. Some online crafters use the hot glue gun on blue or pink foam too.

But how about plastic pieces to foamcore or blue foam?

I did some online research and 3M Brand “77” spray adhesive is recommended. I have some and it worked well for laminating the “paper model” printed outsides to foamcore. However, it did have overspray issues. I haven’t tried it with blue or pink foam. It's not going to be the thing to glue a 1/2" square piece of plastic to anything.

So I did a little testing with three tubed products: Omni-Stick, E6000, and Goop. (E6000 is the recommended glue for all the materials I’m using.)

First, on foamcore:

They all stuck well after just a few seconds of drying. Omni-Stick is best, of course.

Next, on blue foam:

Omni-stick and E6000 worked well. Omni maybe a little faster drying. E6000 is still as “sticky” after a bit. None of these develop their hardest bond until 24 hours--which was what it says on the tubes.

Goop doesn’t stick. An hour or so later I can still lift it off. The next day I could still lift it off. Fail.

CONCLUSION: I will pick up another tube of E6000.

Omni-stick is still the best. Right viscosity, bonds well, spreads well on large pieces. E6000, with it’s narrow nozzle works easier on small pieces. I wouldn’t want to have to spread it on a large wall section--but I probably will. For large pieces I might try the 77 spray although I’ll use Omni-stick while I still have it. Or, if it’s foamcore, Goop would work well and spread easier.