HO-229,
Now that you're here, I'll tell you what my experience has been. No, I dont have any problems with pressure differentials. I think that mod is unnecessary. Mine runs fine pretty much stock using Jag parts. I'm doing 2 more conversions right now and will use a larger bore carb from wacker engines. My stock ryobi flies a 14lb plane (82"ws) with pretty good sport performance. Not unlimited verticle but fun flying none the less. I use zinger 18x8 props and get about 6700 rpm on a tired old wornout engine thats been run hard for about 5 years. All of my ryobis have been given to me for free and almost all of them so far have only needed the carb diaphram to fix it. You really cant beat it.
Edwin