IMO THE CURVEATURE IS A DEFINITE ISSUE. I have had them fall of many times. Sometimes you get lucky but that slight curve reduces the surface area and thus it is a matter of time before whatever is stuck is un stuck. Also I can always tell when theres a medallion on a derby they dont form perfectly and are noticable but I am **** that way.

I say if you want a custom derby hop on line ( ebay, craigslist, etc or go to some swap meats) you can pick up really cool derbys for under 40 bucks and they wont fall off, and theres tons of designs to choose from.

Good luck.