I'm not sure Dave - the old rule-set wasn't exactly crystal clear on that situation to begin with and I think there is still some complicated application here too. 18.4 clearly states that a boat that must gybe at the mark must not sail any further from the mark than necessary but nothing else directly applies to a "gybe".
if you stick with 18.2 a) and b) (since they refer to each other), it's pretty clear that the overlapped, starboard "gybing" boat is the inside boat and is owed inside room at the mark. The only other exclusions to crossing tacks in the zone is 18.3 and it clearly indicates "tacking" and not gybing...so it doesn't apply here.
As you pointed out 18.2 e) seems to give the outside boat some leeway in it's ability give room. While I'm not sure under what circumstances an outside boat could claim the were "unable" to give room, the kicker here is that the overlap has to be developed from "clear astern". "Clear Astern" is defined in the appendix to be the following:
Clear Astern and Clear Ahead; Overlap One boat is clear astern of another
when her hull and equipment in normal position are behind a line abeam
from the aftermost point of the other boat’s hull and equipment in normal
position. The other boat is clear ahead. They overlap when neither is clear
astern. However, they also overlap when a boat between them overlaps both.
These terms always apply to boats on the same tack. They do not apply to
boats on opposite tacks unless rule 18 applies or both boats are sailing more
than ninety degrees from the true wind.
scratch that...I thought this might not apply since the boats would be on opposite tacks...but we're clearly talking about gybes and we're sailing at more than 90 degrees from the true wind...so "clear astern" does appear to apply to this situation...but can you really measure "clear astern" overtake from opposite gybe boats (at the angles we sail)?
