Dan:
Well, I just have to believe your people are also too caught up in the par contest. As a relatively low 'capper myself (5), I am licking my chops at them making that the 17 stroke hole - I will seldom if ever lose, as I'll almost never give a stroke. I'd also LOVE to get a stroke from the scratch on that hole.
However, if the differential is 2nd highest, than 2 stroke hole it should be; although that can and perhaps ought to be fudged a bit since you don't want the lowest stroke holes to so often go unused, as would be the case in normal match play. I believe that's in the USGA guidance also, isn't it?
In any case, it's still curious to me that the differential is the 2nd highest and the difficulty relative to par for both groups is smallest.
This could be explained by the mental aspects of this... neither group fears the hole any more, now that it's called a par 5... for the A's it became a birdie hole, for the Bs it allowed more cushion.
So maybe you just factor this in also and fudge a little? You have good reason to make it the 4 if not higher already, being #18... I can see taking it to #6 just to allow for this mental ease.
And remember, all of the USGA stuff is just guidance - in the end, you guys make the call. So all of this speculation is allowed for also!
TH