ORIGINAL: scapjet
ORIGINAL: FOShowNoClass
..... Just by looking, I think the .91/Dynamax will fit. It will be a heavy plane, but as we've seen people have flown some heavy versions of this. I'm always big on keeping it light. A K&B 7.5 CC and a Macs pipe is supposed to put out around 7 lbs of thrust. That's what I've heard anyway. If the plane is kept at around 10 lbs, which may or may not be possible, It should go very well. I think the .91 version will weigh 2 lbs more. High wing loading, but will fly no problem in my estimation. I'm guessing a .65 or .77 would be ideal. I'm no expert.
Will
I have a A4 Skyhawk JHH, weight is 12.5 lbs with a .77/Dynamax and it flies great, so the same .77/Dynamax on a 10 lbs Hawk should be perfect.
I also have a .91/Dynamax so if possible I will built so that can use both and will see what's best.
scapjet
For those who happen to own a OS.77 and a OS.91, install the backplate and carb from the OS .91 on the OS.77. I bought a stand way off sport scale F-15 from grbaker 6 or 7 years ago that had this combo in it. For kicks one weekend I went through the trouble of pulling the fan unit and swapping the backplate/carbs to see what the differences were. It's like night and day, the OS .91 backplate/carb really wakes up the OS.77.
I also have one of the eBay Hawks and will probably install a Dynamax/OS.77 setup with the .91 carb/backplate.
Rich