60-80? Maybe 200 max. Just don't get too fine. What I did when I did my bicycle it was 160 grit IIRC.

There is this special stuff that you can get from specialty stores that pretty much melts any plastic. I forget what it's called but it's like the opposite of viscous. Anyways, you could probably do it that way.

IIRC it was something like $15-20 for a 3 oz. jar and I got it from "The concrete store" in Vancouver (it's not actually called that but that's the name I know it by I actually forget what the real name is I think it's "the concrete shop"). It's really thin and works on pretty much any plastic I've tried it on. ABS, styrene, PVC, acrylic, etc. So maybe that one might work if the model plastic glue doesn't.

before getting that other stuff i think you should try krazy glue then JB weld.worked well for most of the plastics i've glued together

JB Weld is what I use for when I make portable game consoles, and need to attach plastic peices. Attach, sand, paint, presto. Mmm, looks like its store bought.

You make portable game consoles?

PM me.

JB weld can do anything =)