I can get pretty close to 90 degrees when backing when I was testing everything, luckily most all of the camp grounds we camp don't require that type of turning while backing! My 5th wheel has an extended pin box so that also helps with the cab clearance. As far as squat it doesn't help that I've leveled out the front to the back by lifting the front. So when I'm hooked to the 5th wheel the back will set down pretty good, but I added Ride Rite load leveling bags to help with the squat. I generally run around 60 psi in them to take squat out and they help with the ride quality also.
Been thinking about putting the front back to stock as I'm sure that when the 5th wheel is hooked the truck would set pretty level front to back without the need for the bags. Then just add some air for ride quality.
2002 Silverado 2500HD LB7 CCSB LT
ATP EFI Live, Edge CTS Insight, S&B CAI, PPE boost valve, Pro Fab AIH, AirDog II 165, Mike L built trans, ML-G converter, Allison deep pan, HD trans cooler, Nicktane CAT adapter, 5" straight pipe, Firestone Ride Rite, Cognito braces & HD tie rods, H2's, 305/70-17 Nitto TG's, B&W Turnoverball, Andersen Ultimate 5th Wheel Connection
2015 Crossroads Longhorn Rezerve LFZ36DB