Ys 45 is a fine engine but I would choose something with better low end torque. Irvine 53 is perhaps the best 2-stroke option with APc 13x4 (regular blade, not w). YS 63 and Saito 72 work well too. OS 70 weights too much -- this planes comes out nose heavy.

Mine has Saito 72 with APV 14x4W and 13x6. YS 63 would also work with APC 13x4W.