I'm all for overpowering, but IMHO I would save that lovely Saito 1.50 for an 1.20 aerobat that loves a lightweight 4stroke. Sure the Spacewalker could use the noseweight, but just about any noseweight should fly this plane just fine.

Then again, if you already have the 1.50 and wants to put it into the SW, I'm sure it will fly it great. The airframe is built very well and should take the power just fine. The main problem you'll have might be prop clearance. I've already ditched the stock gear on my SW so I don't know what it will clear. My guess is a 16" prop might be okay.