Thrust to weight ratio required for:

Hover: 1
Fly out of hover: 1.25
Blast out of hover: 1.5
Descending Waterfall: 1
Nice Waterfall: 1.5
Small knife edge loop: 1.25
Nice knife edge loop: 1.5

How much does the plane weigh? If it is over 6 lb, you can forget about 70-class 4-strokers (about 7 lb. of thrust). Maybe Saito 80 or YS 63, swinging 14x4W, about 8 lb. of thrust.

OS has a new 70 4-stroke called "70 Ultimate". It's 16 oz (lightest in class supposedly), rated at 1.2 HP, although the current 70 which is rated at 1.1 HP outpulls the 1.2 HP Saito 72.

If you need more weight to balance, might as well go for a 91 Surpass, which is tested to have 9 lb. of thrust w/ 15x4W.

I am giving you these figures from flying experience (prop & rpm vs. plane weight). Thrust HP will give you results much higher than real life, so use at your own discretion.