Thank you for posting this. I also have this issue and I am going to preform this fix over the weekend.
I used an ego adapter which I had from way back, put it in the drill chuck and screwed the
rda base into the adapter (Note: not good idea to put
rda directly into drill chuck as you can damage the 510 threads).
I used 180 grit sandpaper and wrapped it around the base of the
rda and held it tightly and just let the drill do all the work, Note: I did not sand the ledge on the base of the rda where the top cap sits just sanded the edge of the rda, after test fitting a few times when it felt right I finished it off with 320 grit sandpaper and slightly angled the rda and held the paper so it was just touching the edge of the rda deck and slightly rounded the edge of the top of the rda deck so it doesn't cut into the oring when putting the top cap on, the top cap is much easier to take on and off and the oring is no longer getting chewed.