I had a spare backing plate and after viewing Mr. Browns website I decdided to modify rather than buy. I have since cleaned up the holes using a orange hot icepick. 50/50 before and after using wet sand with 2000 then uberMFer pads and a mix of d300 and m105 more 50/50 with a single pass of d300 and m105 after wet sanding w/2000 grit
I would not as you may weaken the backing plate. its not the same as it being molded from the get go.
I radially oriented the holes varying my order of hole diameter sequentially, thus spreading the loss of plate integrity over the entire width of the plate. So far over thirty hours on this bp without issue. I have a porter cable bp that came from the factory with half inch diameter holes that works great it was just to small for the MF pads. I really am trying to limit my consumption of products, and saw purchasing a new bp as just being wasteful, I already owned this bp and had little to lose if it came apart. I did not want to send another item to a landfill if it was not necessary, I love to buy new things but it has to stop somewhere. Sorry for the rant.
