If you cant see that pic text 978/530/6747
I put that single on my personal a4 fly , bolts up without modding the frame:
shave the valve pin flush with a bevel and you can take it out with a magnet if you ever need to remove it.
Exacto knife will shave the eye strap flush with the body also and still allow it to do its job properly
The vernier wheels lose their adjustment capabilities but the trigger has set screws in it from the factory to limit travel
I used a virtue pmr7 board and mounts from pedro (on ebay)
I Love having the adjustable modes from a virtue, being older and slower it has ramping to.....and day single trigger gets everyone all asking questions...so its added cool.