As far as the Rockers themselves I've heard of it done a few different ways and some fast ways, but I just took my fine flat file, put it in the vice with a soft cloth and slowly work my file out over till it just came down to a nice flat surface. Also can contribute this to triple-r. He told me about it when I first got mine and had the problem. I like to give credit where credit is due and I passed this on as I felt it work very well for me..
I've certainly never tried banana grooves my actually already had them. But when I give it a Ponder for a second I see myself getting a measurement off a stock one so I know exactly where the ends should be so I don't make it too wide. I see myself Drawing the Line on there from where it starts to where it ends crossing the oiling hole. I see myself getting a little round file like for filing chainsaw blades. I see it taking some time and patience, but slowly going back and forth over the little line I made making sure I don't go outside of it from end to end and it crosses directly Over the Hole. Again this is just what I would think...