inboard tank rib hole size for access plate?

I can't find the diameter of the hole to be cut in the inboard tank rib for the access plate. The section B-B' drawing seems to suggest that the hole should be slightly smaller than the ID of the stiffener ring. I do see that the reinforcement ring is 6-3/4" OD, but that doesn't help much.

Someone give me a clue me, please.

Rib cut

This came up recently with mixed responses. The plans show the cut at the inner ring of the rib hole. The photos in the manual show it cut even with the inside of the stiffener flange. Mixed bag of both among builders but I think the consensus was the ring was strong enough to cut the rib flush to the ID of the ring. JMHO worth $.02.

I ended up cutting flush with the ring ID (5-1/4"). Sure enough, Figure 5-13 in the manual shows it cut that way. Works for me.