Gary, I offer you one person’s experience, and suggest that your concerns with the Altaplex may indeed be misconceptions.
I have no direct experience with the Altaplex or FC1, but I am the owner of one of the first Duplexes sold and cannot imagine replacing it with anything else. I’m willing to bet that 30 min. practice pitching the Altaplex in the front yard will dispel any concerns. Yes, the first pitch on uneven ground will be a learning experience, but IMO you’ll get the knack very quickly.
Two of my hiking buddies have the FC2, one UL and the other Platinum. One night camped below treeline but near summit saw a 20 mph wind, fog and rain roll in around midnight. I was warm and bone dry with no flapping in the Duplex. Around 6am the rain let up enough for me to pop out for a pee when I saw the FC2 Platinum’s upwind fly PLASTERED against the inner. The tent was guyed out as well and the design allows and all guys/stakes were still taut and in place. I heard some rustling inside so went over to ask if all was good. My buddy opened the fly enough to talk and he had lost fully 1/3 of the interior volume. He also had to scoot to the downwind side to keep the fly and inner (now essentially one layer) off his sleeping bag. I’ve also have never seen more condensation on the underside of a tent fly. I think the Altaplex will be faster to setup and more stable than the FC1.
Lots of people like the FC, but I would rather purchase an Altaplex that be given an FC free of charge. And if all else fails ZPacks offers a great return for refund.