What works great in situations like this is a brake cylinder hone. I've used one many times for lightly honing seat tubes with corrosion or minor burs at the interior weld surfaces.
I got the damn thing in after lots of emery paper and grease - Thanks
I might take it out and change it now though It's 15 degree rise and looks a bit crap on the Funk :roll: :roll: (hope it comes out easier than when it went it...)