I was thinking of trying this with one of my older engines. i have quite a bit of experience with die grinders over the years mine is almost worn out have to get a new cable for it i've used it so much everyone in the hobby should have on i dont know how anyone wouldget along without one. but i most likely would mount the die grinder and hold the part sounds like a safer way. I have had the die grinder slip and go across a part. not very nice sometimes.
The sleeve and piston for the OS 61 is almost 100 bucks so i would definetly want to do it right and not mess it up. So practice on an old engine that doesnt mean much would be a better idea untill one feels confident that there going to be a good at doing it.
the link ddint work for me for some reason.
If you're curious, have a look in the r/c car engines forum for a modding thread
i found this one witch looked intresting and is the same thread apperently
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http://www.rcuniverse.com/forum/m_5226191/tm.htm
I'll search around and see if i can find the thread since i am curious. i have seeen people modify the cranckshaft's in the rc car engines were they polish the port in the shaft and change the shaft buy Polishing the groove at the end of the shaft to increase the flow of fuel in the engine. but havent seen anyone do such a thing to an aircraft engine.