How about taping a drinking straw to the fin of your Andrews Trainermaster (w/ Enya .60 ) to see if you can drag it across the concrete while inverted?
I left it sticking up above the fin about 1" to try and grind some of it off...heheheh...it didn't work...

After that attempt, I had an Enya .60 with the head fins ground off at a funny angle....