The Spacewalker is a pretty gentle flyer, with thinner strip ailerons. On a 3D or a larger more agressive plane, I would consider them "on the edge".

Those JR's would be perfect for the Spacewalker IMHO.

I'd be more concerned about the receiver pack sizing.

On a 1.20 size Spacewalker I'd be looking at a large pack ( something OVER 2000mAh though John's suggestion IS a good starting point ) if not a pair of 2200 LiFE packs for redundancy. Two of the latter still weigh less than one 2000mAh 6v NiCD or NiMH pack.