Can I convert my rear hope pro2, currently a 135mm, to 150mm with 12mm bolt thru?

no – not unless you have access to a lathe

Nope – your disc would be out of line with just spacers as the hub on the 150mm is wider 🙂

you used to be able to buy spacers for your caliper and axel to keep everything in line , just had to redish your wheel to suit – mr big racing made them (in his garage)

used to have one of their frames back int day !

nevermind, thanks for the quick replys… plan b it is then