Hiya Will...I just used a file because it's such a small amount of material you actually need to remove..I thought about a dremel which would have been quicker but I didn't want to take off "too much"..he he (I used a course file first then a fine file to finish it off)
I've had some stuck piston pins and putting them in the oven has worked for me...Penetrating oil or WD-40 would probably be a great idea too...In my case's it seemed that a build up of "gook" was normally the problem so I think the heat helps soften it enough to remove...
I have to admit that when I first ran into this "interference" I had only seen the YS pistons with the small sleeves...Then when looking at the piston hitting the crank I was thinking you would have to remove half the skirt to make it into a "small" skirt (Oh Crud!!)...Fortunately I took another engine apart to see the factory piston with the small bevel...What a relief!! (Pun intended..he he)
Henry sure makes some good stuff and I'm sure the last time he made these was a long time ago!! When I was thinking I was gonna have to grind off half the skirt I was sorta miffed at his missing on this one....But when I realized the small bevel would work..I just chuckled...Well worth the effort!!
Have Fun...
Chuck