A 11-43 cassette HAL 9000? Now that must climb anything!
Now, I don't know much about Oregon terrain but if you are a road racer, you shouldn't have any problem with the 2x9, people that need triples are either on heavy bikes and/or don't ride/train as much as most racers IMO, but on a go fast XC bike, which the Scalpel is, 2x9 just makes sense.
I also use 29/42 and a 11-34 cassette and it gets me up anything I can climb with the common 22/32/44. I don't see any cons personally but many pros. Front shifts are much slower and clunkier than rear shifts so a 2x9 usually means less front shifts, more rear ones. And rear shifts can handle shifting under power much better than front shifts. With the 42 big ring, you can stay on it most of the time and dropping to the 29 only on very long/steep climbs or slow technical sections. Sure you lose a few low-end gears compared to a triple but it actually helps sometimes because you don't want to have a too slow cadence when climbing so if you are out of gear, you just pedal and go faster...
It also apparently cuts the chainsuck risks but I cant say, never had too much trouble on 2x9 or 3x9 unless my drivetrains are really dirty.
You also save a bit of weight on the crank but I saved more by going with a road derailleur, it works just as well as a mountain unit but it's much lighter. I use a Dura-Ace 7700, it's the last 9-speed Dura-Ace so the cage is a bit wider than 10-speeds. This allows you to use more gear combos without having to trim the front derailleur, not a big issue with Grip Shifts but it can be helpful with triggers. Mine in 31.8 clamp style weighs 86gr, almost half of what a XTR weighs and currently, XTR are the lightest front derailleurs available. Anyway, weight is not the first reason to go 2x9, a better gear range and better shifts are much more important if you ask me.
