I have had off-and-on lower back problems since tearing a muscle in my left lower back when I was a teenager, and have avoided riding anything with forward controls based on other people's comments about how they kill your back. Actually, I avoided cruisers altogether, for that and functional reasons.
Within the last year or so, I have ridden my cousin's Star Raider several times, for about two hours at a time, and was really comfortable. The scooped-out shape of the seat is almost like having a mini-backrest that kept my pelvis from rotating back, keeping my lower back straight. The seat is also large enough to give a lot of support on the back of my thighs, spreading out the load very well. With a small shield, I could tour on that bike. Honestly, I was surprised at how well the bike worked as a motorcycle; not as compromised as I thought it would be, given the way it looks.
Would I own a bike with forward controls? Yeah, but not the Raider. Don't like the chopper styling. I do like the Triumph Thunderbird Storm (have ridden a T-Bird SE), and the Harley Fat Bob. With the right seat, forward controls would be fine for a cruiser/weekend tourer for me. My 6'4" tall 36" inseam frame likes the legroom. The only adjustment I would have is the time it would take to get used to finding the pegs when pulling away from a stop.
Problems cannot be solved at the same level of awareness that created them.