A Morris GWB is better on a good strong 40 to 53. A 60 would add too much weight. If you are not at a really high altitude, then don't go that way.
The OMP 65 Yak sure looks nice, and they give free shipping. There is a construction thread on RCU with a few Pro Bros participating. If the plane comes in at the weight that OMP says it does, most 60 size two strokes would be fine for it.
If my YS91 had not already been promissed to another project, I'd be looking more seriously at one. Maybe Christmas...
Tail Twister ... don't you can use wings nuts for your motors on the mount? This way when your at the field you don't even need a wrench to swap your motors. Just put a little ummph into it when tightening.
The YS 91 shakes like an SOB! I use 8-32 hardened bolts, and I've sheared even one of those. I don't hink I could afford all of the lost wing nuts.
Maybe the Yak can be for next Christmas. I've already got a few new ones to fly this season. I kit bashed a GP G-202 into what should be a good 3D machine. I built an EF Mini 3D ARF. My 91 is going into a Super Cub that I'm now ready to cover. I'm starting my 3D electric project in a day or two. I'm goint to sell my Funtana and put the Saito 72 back in the Sledge, and get my ST 51 back in the Hot Hots, which was repaired this winter. All of that from about October until now. It's been a busy winter, and I don't think I'll be building again for a while. I'm plum tuckered out.
Now how about that 65 inch Yak ARF? I might could handle that...