The wing drilling session was made significantly more stress free thanks to the loan of a clamp from Gary Smith, a UK RV builder.
It comes with three bushings :
* 1/8" * #12 * 5/16"
As we wanted to ream the hole we used a 9/32" drill after the #12 and then reamed 5/16".
For UK builders who want to borrow this make a plea on the RV Forum to see who is the current custodian. If you are elsewhere and want to make your own my only suggestions would be:
* Make the main bushing base 5/8" radius as this will then equate to your minimum edge distance * If you intend to ream make a 9/32" bushing.