So, we recently got a travel trailer with a tongue weight of 820 pounds. gvwr is 9600 but the weight typically stays around 7600-8000 as i don't really carry any liquids in the tanks. I've noticed a 4 inch sag in the rear even with a weight distribution/anti sway hitch. I'm around 75k miles on stock tss suspension on a 2014 double cab and haven't noticed any leaking in the shocks but was curious about upgrading to bilstein 4600 or 5100 series shocks to try to solve the issue before going to air bags. Kicker is I don't need the lift or level of the 5100's as I already have a 2.5 front and 1 inch rear lift level but they are block not suspension lift and I have a Transfer flow 46 gallon tank that, when full, causes some lean to the left. Would I be better off just going 4600 for the stiffer shock and same ride height or should I go for the 5100 and basically corner balance for the additional weight of the fuel since from factory i only had the 26 gallon tank?