Interesting G&T. From my perspective on the 74, only the Trent is crossloaded (on a specially designed 196*125 pmc thickness pallet) all the other RR big fans are can be loaded onto a 10 (sandwich pallet) or 16-20. 524 or 535 makes little difference in that sense.
The ONLY thing that interested me was the over WIDTH of whatever engine being longitudinally loaded. I'd often have a P1P (PAG) 88" pallet built to place opposite a 524 fan.