Hey Dave as you know I am doing Echo and Poulan conversions. I have never made a prop hub longer than two inches that did not have shaft support through it. One Echo I am just finishing has a shaft that is about 2 1/4 long or so. If the engine needs to be out any farther than that I always use a stand off of some sort. I would think that you should be able to do the same with your engines. Never had a Ryobi though so maybe I am wrong. Let me know on those carbs so I can get them out to you.

Tim