Adding standoffs to existing aluminum motherboard tray?

So I have the chance to get my hands on a Jonsbo UMX1, which is an aluminum mITX case that i really like a lot.

I realized that with some tinkering, it is very likely that I can get an mATX system in there - the chassis is big enough for an mATX motherboard to go in.

The only issue is trying to get the motherboard standoffs to fit. I've been looking up the mITX and mATX mounting holes, and it seems I can use at least 2 holes that are common to both formats. Howver, I'll definitely need more standoffs.

The problem is that the Jonsbo UMX1 is aluminum, and has no standalone motherboard tray - apparently the motherboard tray is the side panel. So drilling is not an option. Soldering steel standoffs to aluminum is also too complicated.

Anyone has any good suggestions? Would some sort of resin/epoxy hold the standoffs in the right position?

Thanks!

Rivet/bolt/etc another plate on and mount them to that?

Resin/epoxy on sheet metal would be a real bitch, even if you sanded it rough. I wouldn't recommend that if you ever wanted to move the case, the flex could probably break the contact patch.

Unless you're using a weird funky mATX motherboard, all four mITX standoffs are compatible with mATX.

You could always find a pice of aluminum that is thick enough to put the standoffs in and then jbweld it to the original. Jbweld is stronger than epoxy and can be drilled and tapped just like metal.

What about JBWeld? It's pretty much made for this exact purpose. Failing that, just about any epoxy type glue ought to work.