Get the Z fare. If you read FT enough, you'll hear about the SWU/W-fare "roulette". You don't need that. If you get the Z fare, you are buying a business cabin seat. You won't have to worry about battle-field upgrades at the gate, nor about irops; you'll be sitting in C.

A Z fare is restricted, yes, but so is a W fare. A Z fare won't get you "arrivals" access, but it can be upgraded via UFC or miles + copay to NF. I've had good luck with this. And a Z fare on LH can be upgraded with a SWU (paper SWU, requested in advance, day of flight).

If you have left-over SWUs, collect 'em and trade 'em with your friends on FT. Or upgrade your spouse. Or yourself on a long-haul domestic (BOS-X-HI), e.g.

They work just as well as "extra" CR-1s.