I find that the manufacturer's recommended engine range doesn't usually give me the performance I'm looking for. I want to know what size 2 stroke engine will give me excellent 3d performance and unlimited vertical. My plane is a 67" yak that should weigh around 10 lbs. The manufacturer suggests between a .61-.91. From past experience, I know this won't do the job. I don't want to go 4 stroke, so please don't tell me that.

120 size is peerrrrfect, i love that yak. i m getting one soon.

10 pounds? That OS 160 zone.

ROFL... OS 160 2 stroke on a 60 size plane. Might have a slight ballancing problem ... along with the 4 pounds of fiberglass to keep the firewall attatched to the plane. [:P]
I have an ASP 1.08 in an Ultimate ... and I've got an OS 1.08 FSR in a U Can Do. Both spin an APC 16X4W and both have unlimited vertical. The Ultimate weighs about 13 pounds and will go vertical as soon as the tail clears the ground. The UCD weighs in at just under 8 1/2 pounds, and I can't keep it still.

Run OS 160 on 2 meter 10 pound pattern planes all the time. However I am also the one who put a 160 on a Showtime 90 and it was INSANE!!!! with 3 servos in the tail and zero balance problems.

Im with YNOT, A 120 will probably give you unlimited vertical, But it wont punch you out a hover like I want it to. ("exellent 3d performance") I hate a plane that struggles out of a hover!

get a 160 and use throttle management. don't go full throttle down line and pull up elevator, use it sensibly. i mean you don't need to fly your whole flight at 3/4 throttle. 120 will be ok to but 160 will definately give that extra bit your looking for. and i fiberglass the insides of my firewalls now anyway before i even start building my plane....just in case...and it only takes like 15 minutes and 5 bucks or so.