Which Distance to Ride for the TOWM

As I mentioned yesterday, I’m thinking about riding the Tour of the White Mountains on October 6.  Actually, I’m more than thinking about it, I’m fairly committed to it.  The next big question is what distance to go?  The choices are 41, 52, and 66 miles.  The 41 and 52 ride routes I have ridden much of, just not all at once.  The 66 adds a section I’m not familiar with.
As a single day’s ride, I’ve done 35 miles a number of times.  I’ve also done the 24 Hrs in the Old Pueblo twice, and in so doing logged 87 & 122 miles in a 24 hour period.  What I’m having a bit of trouble gauging is my current fitness level.  I feel about as in shape as I was when I did the 122 miles as part of a duo, but possibly better.  At that time I really wasn’t in great shape.  The next year, when I did 87 miles as part of a 4-person team, I was definitely in better shape than I am now.
52 Mile Route
I talked with Chris Z about it today, and he seemed up for the event.  He’s done a number of longer road rides and noted, “66 miles on a mountain bike is a long way.”  Well, yes it is.  But the TOWM is on relatively tame trails.  At altitude for sure (7000+ feet), but nothing remotely technical.
For now, I’m inclined toward the 52 mile distance.  It offers some single track I have yet to ride, less forest roads than the 41 miler, and an added climb in the beginning to get me thinking, “Will I be able to finish?”, in the first 10 miles.  That’s what these events are all about.  Finding a way to finish.