I agree totally with your situation - I've sold off all my YS's this past year (91 and 63). They just gave me headaches - I'd rather be flying and practicing rather than fiddling with those things all the times.

Unfortuantely, there's not much left to choose from anymore in this size range. I have 2 90 size pattern birds - one a Synergy 90 3D and one a Kyosho G-Trick. I picked up a OS 91 FS-II w/ pump and have flown it on my Synergy which is A LOT lighter than the G-Trick. It could still use more power. Debating on whether to go OS 91 FX w/ pump but hesitate because 2 strokes are messier and noiser and haven't heard the best things about the 91 FX.

The good news is that Webra just introduced (or reintroduced?) their 91 speed which looks great. Still no pump but we'll have to add one ourselves.

What to do? Either optimize kits for the 91 four-strokes (make them lighter or smaller) or explore other engine options.

I'm debating of designing a plane for the everyday engines in this size range, primarily that OS 91 FSII-P that I have. Would be laser cut, of course.

Just my thoughts... sounds like we're thiking along the same lines.