I'm about to book an award that has a leg BKK-NRT on 3/25/2012, on TG using UA MP. The website shows no availability in J cabin, and will allow a 'mixed cabin' saver award for Business.

I checked out that flight on Expert Flyer and it looks almost empty, perhaps they are blocking/restricting inventory for now, but wondering about this waitlisting option.

If I book it in Y Cabin, and don't waitlist or check back I assume i'll be sitting in the back, regardless of the amount of miles I redeem? There wouldn't be an auto upgrade on this?

Wondering if I can book it with the waitlist (I have no status with UA) option, or if I book it as is and call back when seats open up, will they be OK with putting me into the J seat on this award?

Guess I am asking, if I accept mixed cabin, will they force me to stick with it, and if not can I use this WL option?