Is it possible to hubstack both sides of a Project 2 or any other Project?

You can hubstack a Project. You can use the FHZ stack kit, but it is more inconsistent than using the axle and hubstacks from a PGM.

I suppose you could do the same with a Project 2, but I don't think the details have been worked out yet. If I had a PGM, I could tell you, haha. We will know soon enough though.

but can you hubstack the axle half and the non-axle half?

Yes, they can be completely hubstacked.

Thanks! Now I can either order a PGM or buy a ceramic kk for my Dark Magic...

I'd go with the PGM. DMs are nice and all, but PGMs are great. Course you could also contact buy a replacement axle kit for an 888 and hubstack upgrade for it as well to stack it?