I have been balancing rollers for a few years now, mostly Chebbies. There is a substantial improvement that can be made.
On the BB at least, the pump cam can be removed or a wing thing made. At the rear you may not be able to achieve nirvana but do the best you can with what you have to work with. I use 3/8 and 7/16 HM to get it the best I can. Working around the oil relief holes is the troublesome part.
reduction of imbalance is a big improvement.
The funny thing is that I wrote an article on this issue showing what I found originally and how I went about the mods. I originally gave it to DRO back in their early days but no one thought anyone cared about this. After all, it's such a little thing, right?
I will see if he still has it on file, update it and get him to print it. Maybe something there will be of use.