Okay, after much messing around with the math, it looks like I'm going with...
For the pseudo-decoction part of the mash, .5lb Wheat, 1.3lb Dark Munich, .5lb Pils, .7lb Carawheat, 1oz Carafa. Make this a thick mash at 1qt/lb so mash in with just over 3qts of water at 111F to get a first rest at 104F.
For the main mash, 3.5lb Wheat, .7lb Dark Munich, 1.5lb Pils, .3lb Carawheat, 1oz Carafa. This is a thinner mash at 1.5qt/lb so mash in with just over 9qts of water at 108F to get a first rest also at 104F.
After a 20 minute rest on the first mash, stick it in the pressure cooker and give it 15-20 minutes at 15psi. Once it's cooled back down to 212F and the thingy drops, combine it with the main mash. Math says this should get the main mash up to 132F so I'll also add a little over 6qts of water at 205F to get the final rest to 155F.
Vorlauf, drain, sparge with 3.5 gallons of water at 174F to get sparge temp of 168F. Carry on as usual from here on out.
We'll see how it all works out tomorrow.