Here is my ryobi timeline:
1- Purchace Ryobi trimmer from Harbor Freight.
2- Tear trimer down
3- By conversion parts from Jag engines and wacker aviation.
4- Rebuild engine.

Trouble:
Jag engine mount to long for model-
Solution:
Put it in the parts box (sorry JAG) and ordered a custom plate mount from wacker.

First Test:
Engine ran OK - 18X6-10 @ 6400 RPM- Time to mount it in the plane-

Trouble:
Carb has high end adjustment only, and will not draw fuel when pointed up. [attempt several fuel configs to solve] failed.
Solution:
Scour local shops for walbro carb- [Found Walbro WA-55-1] Difference= external vacume system and larger fuel inlets + larger opening. I tapped the back plate and mounted a pressure fitting.

Engine Test:
Excellent performance now up to 7200 RPM no fuel draw issues at all. New vacume system is excellent..

Trouble:
Fuel line to close to muffler.
Solution: Install simple heat shield (pending)