Best way to raise FW

My opinion--yours may vary. I went through the same problems in 2013 with a new fifth wheel. Suggest first investing in a bunch of boards. Actually back the trailer up on increasingly high stacks of boards until it is level (on level ground of course.) This puts the trailer in the exact position that you're after and you can then get an exact measurement of the lift needed. My measurements changed a little when I did this. I needed 3.5" of lift which I got with a CorrectTrack and by going from 15" to thin 16" tire (LT215R85-16) because I didn't need all the lift of a 235R85-16 tire. Also a 235R85-16 tire may not allow enough clearance between the tires or above the tires. The CorrectTrack was a tough installation, and I don't think that I would do it again. I'd just find a qualified shop to build a sub-frame. Finding such a shop is tough however. You can probable google my signature or CorrectTrack to find the old stories.