The new ones still only give me 1/2 inch length from the control surface to the center of the hole where the clevis is inserted. Is that going to be long enough for a 3 meter sailplane?
On average, you'd probably want a horn that's close to 1" tall. I just measured the horns I use on a 3m and the outer hole is 7/8" from the bottom of the horn. The throw I'd get from that 7/8" will be greater by half the thickness of the aileron it's bolted to. So that horn can deliver one inch of lever. It's only a medium duty horn. Heavy duty horns are taller.