When in doubt, just pin it.
Search inside pics of the lodge on this hunting gear forum.
I have the same truck as you and I have a 8ft Camperette. With it fully loaded with gear, water and 3-4 gerry cans of gas and myself in the truck I just get to the weight rating of the truck. Its small and you have to duck to get in the door and inside height is about 5'10 but sleeps two comfortably. It had a ice box that I removed and just use a cooler now. Also has a two burner stove and furnace that I yet found a reason to use. It has a bit of an over hang at the front that becomes a sort of bunk for kids. I just use it for gear storage and the bedding and bags. Got it for $500 and put another $200 into it and I would not sell it for $2000. I went from sleeping in the canopy of my truck on a plywood bed with gear underneath and it worked but the camperette is like the penthouse suite now.
The best thing is when I take it off the truck and bolt some heavy duty castors on the bottom and lower it to the ground. I can easy roll (on concrete) to where I want to store it. You could easily roll it into a garage and push it into a corner for the offseason.
BHB
With a 6.5ft truck bed you could make something like this and stay comfy: https://youtu.be/_0c-YsY5XUw?t=20s
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Best getting a wall tent and a small utility trailer. Campers and trailers are notoriously miserable once the weather turns cold and wet. Think -10 or so with rain , hail ,sleet. trailer get cold and clammy. no amount of propane heat dries your clothes and warms you up. Been there, had a wall tent and cots and wood stove last few years. No comparison, I can put my quad on my 12' trailer, load it up with firewood at the end of the hunt. No matter what the outside conditions are I always can get warm and dry. I could not say the same when I tried hunting out of my trailer.
Not sure what kind of trailer you were using Longwalk, but I have had campers and trailers for hunting for the most part of 40 years and yes it has gotten moist when north end of the island pissing down for days, but never a problem and propane can be moist too, so a electric space heat and generator (which most of us take) can keep things dried out. Also in -30 moose hunting , there is no setting up a tent in a snow storm it is pull over get in camper or trailer and sleep. Also do not have to dry out a tent before packing it away for season. Even saying all this I think wall tents are amazing, lots of room, wood heat is always the best for drying things too and warming up also. If getting a tent when you decide the size you need , get one size bigger , sort of like when building a deck on your house, more room is better.
"People who know the least always argue the most."
"You should not use a rifle that will kill an animal when everything goes right, you should use one that will do the job when everything goes wrong."
The moose is loose lodge with the wood stove, minus 30 while big buck hunting 30 inside with no flapping canvas, mice. Once the door is closed you have no idea what the weather is doing. I had a wall tent for 25 years and it was awesome but the cargo trailer as I get older does the job. Younger guys get in a wall tent and pay your dues lol.
I used a trail sport ultralight a couple years of years, then moved on to a toy hauler. Did one late fall trip in my ,Arctic fox. Always had condensation issues. That being said I never used electric heat. always had a genny but always had windows and vents cracked to reduce the constant stream of water running down the windows. Granted a tent is a PITA to put up, take down and to store properly, but once it's up the warmth, comfort and useable space is unbeatable.
Trying my luck this year with a 7 x 14 enclosed trailer with bunks and a Dickinson diesel heater. Hopefully enough dry heat to keep warm and dry things out.