The split should be 77/23, in my opinion. Here's why:
Assuming that both WAMUQs and WAMPQs both satisfy the "old and cold" rule needed to maximize the $17 billion in NOLs, these are what the numbers look like to get a 51% ownership while giving WAMUQs the smallest percentage possible to do so:
Under the 77% preffered / 23% common split
WAMPQ 40.5% x 77% (the total amount that should be owned by preferreds, imo) = 31.1% 31.1% x 95% (the total amount owned by all of equity) = 29.6% ownership of NewCo
WAMUQ 23% (the total amount that should be owned by commons, imo) x 95% = 21.8% ownership of NewCo