Would like to hear from anyone who has used the Zephyr seat that Rans offers. Can I use a 'shortie' pan or carbon pan with it? The Zephr looks like it would be plenty comfortable, but not quite as handy when you want to hang a day pack on it.
WHEELS: What is it with all these spokes? The stock wheels on this and many other bents come with 36 spokes. With 20" wheels this is way overkill. I've built a couple of pairs of wheels using Velocity Aeroheat rims and Ultegra hubs 28 in front and 32 rear, and that's for loaded touring on a couple of DFs I ride. (small wheel fan) Am considering the Thracian Wheels they offer, but they're not cheap. Another option I toy with is building some 451 wheels and changing the brakes to calipers. There is room, but the fattest tire would be 1 3/8" and maybe no fender clearance with that. Swithing back and forth would be a pain, 'cause I'd also have to change the brake levers. I have been very pleased with the Primo Comets; they're fast yet ample in section to handle gravel roads aired down a bit. We have a lot of gravel road riding here in Vermont.

Haven't used a zephyr seat. The RANS instructional guide pictures show what looks like a cf seat pan. The seat pan is included.
I switched to the thinner, lighter seat cushion/cover from the stock fat blob of jello on my TW.

Seat: I have no experience with the Zephyr seat, but I've heard some say it wasn't as comfy as the standard seat - rails hit them in the wrong spot. You can drop some weight by replacing the stock fat seat cushion with the thin one-piece padded cover. I'm thinking of making a carbon pan for my V-Rex with the thought of dropping a little more weight. If you're going the replace the whole seat, consider getting the Bacchetta Euromesh seat.

Wheels: You're right, 36s wheels are massive overkill on a 20" wheel. I have disc-specific Thracians on my Baron, and even they are only 24 spoke front and back. I am considering putting a set ov Velocities on my old V-Rex24. The biggest problem with the 406 size wheel is the lack of available skinny tires. Unless you're looking to go skinnier than 1 1/8" then there's not much reason to convert to 451. Yes, 451 is a little larger diameter, but not enough to turn a Rocket into a big-wheel bike.