RE: Goldberg Ultimate 10-300 build
I had a Os 1.20 4-stroke (basic version) on mine, and it did actually hover at about 3/4 throttle. It did not however recover vertival from hover, so I have bought a Saito 150 for my next build. It should be more than enough power! (Unfortunately, I have not had enough tine to finish this CG Ultimate yet, but hopefully over the summer... I'm finishing an 1,9m Ultimate in the meantime).
A friend of mine had an Os 1.08 in his Ultimate, but didn't really enjoy either sound nor performance. He changed to a 120 4-cycle, and did not regret the change!
With the heavier Os 4-cycle engines, I found that I had to put my battery way back to get the desired backwards CG. This is "essential" for those really fast snap-rolls and hover manouvers. Much more fun to fly with the CG as far back as one dares... (But DO get to know the plane with the correct CG position first!!!).