I derimmed my 20 long while it was in action, luckily my edges were decent, none are sharp or ugly, but not sure how yours would be, however sealing the inside to make sure nothing falls in is easy when you sand it down, should you have to. its easy and it is fun, the trick is going slow for your first one, my first derimming i took an hour, now with confidence it takes about 5-10 minutes for the top rim of a 40 breeder and about 15-30 for the bottom.
