I’ve had a couple of sets of 5100s. I’ll give some detail here.
2006 tundra, front and rear. Rear had a 200 lb fiberglass shell. Front, I dialed in half of the available lift, about a 1” rise. Truck ran stiff before, and stiffer after. The front shocks did demonstrate digressive valving well, however, because they would “let go” during a hard hit and stiffen back up once neutral again. The control overall with the 5100s in this truck was superb. It had a LS diff in it, and was easy as cake to drift in the rain, all day and every day.
2018 F150. I towed back then and the oem shocks were done at 18k. Put 5100s on the rear, no lift. *I think these would be much better with a lift, will explain.” First, the compression and rebound are notably different. They have more compression damping than rebound. They were ok new but 30-40k in, the rebound damping, which was low to begin with, went to nothing. If you drive over chop, it pops the truck up in the air quickly and then it kind floats its way down. The effect on concrete interstate is nauseating floaty pogo stick. It was exacerbated by an additional feature - about 2” from the bottom of travel something internal changes and the shock gets much firmer, like an additional damping factor prior to bump stops. It made it feel like the truck was regularly contacting and pressing off the bump stops, when in actuality it wasnt. This added extra oomf to kicking the tail up in the air. Had the truck had a 2” lift in the rear, I doubt it would have been apparent. Anyway, the two characteristics combined gave the tail end a weird personality. It may very well be that it would be a fine riding shock, perhaps one of the best, if it didn’t kick the back end up so readily.
I tried a replacement set of 5100s and they were better but by then I was already kinda sensitive to the weird compression/rebound tuning. It’s while doing the install I realized the difference at the last 2”. I didn’t keep them and went to fox. fox was amazing with a load in the back, and are linearly valved. They were therefore far more predictable. But they were very stiff without a load. Later upgraded to fox shocks valved by accutune and was exceptionally pleased. Rode like an accord on the road, and I could dial the stiffness up a notch or two when loaded for a long distance. Granted, we weren’t talking about 5100 prices at that point, but I was tired of dealing with it. I didn’t regret the fox purchase, and they matched the character of the front OE shocks very well.