Specialized can write whatever they want on the sidewall, but that doesn't make it true. The 2.6" Purgatory simply isn't a 2.6" tire - it's smaller than some nominally 2.5" tires. On my 36 mm (internal) rims, it does not rub the stays. The tire's box lists the actual width of the tire on various rims and all measurements are well under 2.6", so Specialized even acknowledges the problem - and these listed widths are still a tiny bit short of the actual width.

It's possible Specialized has become more honest with their sizing on the Eliminator. Would be easy to do: just use last year's also-fraudulently-sized 2.8" casing and rename it 2.6".

I can only reiterate what I wrote earlier:

• 2.6" Kenda Nevegal2: Rubs frequently, even with at least 1 mm trimmed off the outer edges of the side lugs. Slightly oversized. Visibly larger than the other tires.
• 2.6" IRC Tanken: Rubs occasionally. True to size.
• 2.6" Vittoria Martello: May rub once in a rare while, but not enough to worry about, if at all. Slightly undersized. Tread is clustered toward the centre: looks like a 2.4" tread on a 2.5" casing.
• 2.6" Specialized Purgatory: Doesn't rub because it's not 2.6". GRID casing is fragile, too: three punctures in about a dozen rides.

And yes, this is charging hard.

My recommendation is the Vittoria Martello as largest tire that will fit with minimal rubbing. The combination of large casing and narrow tread makes full use of the available space and the tire has a nice ride quality, especially for the rear.

 Yeah, it's working for me. Unlike photos of trails, this looks steeper than it is! Most saddles are concave upward - i.e. the rear slopes down, while the front is pretty flat. This saddle is flat with a downward-sloping nose, so the rear is actually at a similar angle to saddles that look fairly "flat", but the nose makes this look very downward sloping.

Long story short, I think this profile makes sense for mountain bikes, since the nose is less likely to hook your shorts and if I ever have to slide forward to maintain balance on a steep climb, the nose is at a better angle than if the saddle were concave upward.

 Depends who's measuring!

Tightest spot is on the seatstays, beside the side lugs. Clearance elsewhere is always adequate.

• Specialized Purgatory 2.6": Loads of clearance ... because it's not really a 2.6".
• Vittoria Martello 2.6": Adequate clearance. Lugs are clustered toward the centre of the tire, so they don't stick out as far, providing good clearance.
• IRC Tanken 2.6": Tight, but okay.
• Kenda Nevegal2 2.6": Trimmed about 1 mm off the outside of the side lugs; still buzzes the seatstays frequently. It measures 2.6" on a 30 mm rim and about 2.65" on a 36 mm rim, which is what I mainly used for testing.

 Yeah, and not much has changed, other than tires and grips. Big changes planned for the off-season, though: going to swap the frame to the latest version for more stiffness, tire clearance, and better rear triangle alignment, and going to swap the fork. May change the shifter, too; undecided on the derailleur.