It took me a little while to figure out what they intended, at least on the RV-7A. The idea is that the bulkhead fitting sits on the landing gear mount. The hole in the bottom skin is just a clearance hole. On the 7A there is a gap between the bottom skin and the gear mount that is what had me confused.
I did eventually see the larger hole callout on the drawing for the 5/8" hole. I drilled one hole this way, but I had a issue where the hole in the bottom skin wasn't perfectly aligned with the hole in the gear mount.
I think the better way is to work up to the larger hole in the skin. Start with a hole that the bulkhead fitting can pass through then use a little (3/8") sanding drum on a dremel tool working up to a larger (1/2") drum to get the clearance that you need. This approach worked well for me. I assume I'll be filling around the fitting with sealant of some kind later on.
Hope this helps.
2018 Donation Paid
RV-7 Fuselage in progress
* Fwd Fuselage Complete
* Mid Fuselage Complete
* Aft Fuselage Complete
RV-7 SB Wings
* Both Wings fully skinned
* Fuel Tanks Complete - No leaks finally
* Ailerons Complete
* Flaps Complete
RV-7 Empennage - Complete (a little fiberglass work left)
Vans Training Kit # 2 - Complete
Shop Setup - In Progress (Gathering Tools, Never Complete)
RV-7 Preview Plans
Vans Training Kit #1 - Complete
EAA Sheet Metal Class - Complete