So how would one determine the right Derringer units to replace factory turnbuckles for a 2010 Tundra DC and a 2014 front dinette Hawk?
Edited because, as Vic points out below, the only Torklift product that allows a short enough tiedown for our campers is what’s called the Derringer Handles on their web site.
If you wish to have a non-loosening tie-down that can be installed faster (using a well designed quick release device) and don’t want any additional flexibility in the tie downs, then the Derringer handles are what you would use. You would need to separately obtain half-inch threaded hooks of the right length for one end of each tie down, and one way or another lock the threads of the half inch hook so it can’t come loose.
If you are trying to introduce additional flexibility in one or both pairs of tie downs, the only product from Torklift that looks like it could fit into a short enough turnbuckle assembly is the Basic Springload. They don’t sell them separately on the web site (they include chain and a turnbuckle), but when I talked to the company a couple of years ago the guy on the phone seemed willing to sell me the parts separately.
In my opinion, for a slide-in FWC installation, whether you really need the flexibility of spring loaded tie downs is determined by how much your truck bed twists in response to the diagonal loads applied based on both the flexibility of your truck and the type of driving you do. If I thought I needed flexible tie downs, I would only install them at the front. You don’t need or want all four tie downs to have a lot of flexibility or your camper may move more than you want.
The rear flare of the camper is wider, and due to that I think that’s the end you want to keep planted in full contact with the bed if the bed is twisting. The front of the camper tub is less than 48 inches wide, so that’s the end where I would allow some lifting one or the other corner to occur when the bed twists so that the camper attachment fittings and the camper are not not forced to move with the twisting bed floor. Forcing them to move with the bed floor when the bed twists excessively would introduce very high tie down loads, possibly tearing out the camper fitting or bed eye. If the tie down doesn’t fail you flex the camper frame excessively, potentially causing damage to the camper.
My GMC hd truck is very stiff in twist and I haven’t worried about needing additional flexibility in the tie down system. Some other truck types are more flexible in twist, and might cause you to consider adding flexibility. I think for most people though who have a more flexible truck type, their careful driving habits still prevent them from really needing spring loaded front tie downs. Nothing wrong with being conservative and having that flexibility, though, as long as it doesn’t allow your camper to move around excessively in normal driving. The right kind of rubber mat really helps for that.