@Anaro - I'm not ignoring other's advice, but all the "official" sources (distributors and manufacturers) I've talked to on a WDH confirm that it is designed to distribute weight evenly to the front and rear axle of the tow vehicle and will distribute very little (if any) to the camper axle since the camper already rides even. This doesn't help me, as my payload weight is the same. My thread title is about decreasing tongue weight, not redistributing it to the front axle, which a WDH would be very good at. Sorry if you misinterpreted my intentions. I'm on a fact finding mission
Here's what I've done recently...
I measured the distance between axle and tongue for each of my assets: LP tank, battery, hot water storage, and even a Prorac bike carrier (where both front and rear tires would sit). This gave me an estimated tongue weight for each asset, and amazingly it is almost identical to my actual tongue measurements - so I'm confident in using this to estimate what adding or taking away something will do to my tongue weight.
Here are the ideas I'm investigating in case it helps others:
The prorac system doesn't help me much on tongue weight. Adding in the weight of the rack itself, 2 bikes goes from weighing 68 lbs in my truck bed to 57 lbs of tongue weight on the Prorac. Not much of a savings. Even 4 bikes goes from 136 lbs of weight in my truck bed to 97.7 lbs of tongue weight on the Prorac. For me, this isn't worth the effort - so I'm instead looking at a permenant rack on the roof of the popup to place the bike weight mostly on the camper axle. This could get ~140 lbs out of my truck payload and onto the camper axles - a huge difference. Sam @ Flagstaff was very helpful in identifying exactly where the framing is. Contrary to what most dealers do, he does NOT advise mounting the rack to the very edge. Instead, the best part of the roof frame is just inside that corner edging. May be different for your pup, but wanted to pass along to check with him before doing anything.
I'm reconfiguring my LP rack to allow me to only take 1 tank for weekend trips. Immediate 31.5 lb tongue weight savings on a 20 lb propane tank (38.7 lbs for base tank weight plus propane, 81.8% of which is transfered to tongue weight). 1 tank is sufficient for 90% of my trips, even running the furnace fairly liberarly at 10,000 feet in the Rockies and using it to run my fridge.
I might go with only one battery for shorter trips and bring along a second for longer ones. If I do the 2nd, I probably won't go in parallel, as one battery might be "older" (have more charge/discharges) than the other. Instead, I'll switch from 1 battery to the 2nd halfway through my trip. My batteries are right in front of the box, which means 72.7% of their weight is transfered to tongue weight.
For me, maximizing the amount of water I take along is key since I'm boondocking 100% of the time. So, I'd rather give up the 2nd LP than hot water weight, which for me is 6 gallons or 50 lbs, of which only 24.25 is transfered to tongue weight. So, I'm going to try and keep the hot water tank full.
In short, once I understood the exact weight that each asset placed on the tongue, I could make proper decisions on what to keep and what to forego. For now, while my kids are younger, I can technically roll up to Yellowstone fully loaded with 2 LPs, 2 batteries, etc. But when I don't need all that stuff, I'll leave it at home and simply pack a few items like the cooler or a few heavy bags in the popup to give me ~100 lbs fudge factor on my truck's payload capacity.
When my kids grow older and add weight in both themselves and heavier bikes, I'll look at the Prorac permenant install bike rack to put all that on the camper axle rather than the truck's.