Juganought I guess I don't know how to explain it better but I will try again.
First bolt a set of rear rims together just as you would for the rear of the truck.
Next place a hex drive in the rim set and as Thor said put a bolt or an old axle shaft threw it and have the sub sticking out on the side with the hex.
Next chuck it up in the drill press or mill turn it on slow and take your preferred cutting tool (mine is a hack saw blade) you will be cutting on the out side rim. Cut along the outer bead seat of the rim cutting off the center and outer bead.
You will be left with the inner rim and the inner bead of the out side rim as shown in the pic.
Here are some comparison pics of a standard front axle and a TLT-1 the standard axle is approximately 7 in and a TLT-1 with the inner rear rim is 7.125 in and my custom rims are 7.75 in and my new custom rims by ihbuilder are 7.375 in on a TLT axle
A TLT-1 is 175 mm hex to hex and the narrow RC channel is 166mm hex to hex so it is a good bit smaller but for the price I will stick with what I am using. Supper single rims and tires on a 1:1 are wider than normal but I think mine are a bit too wide so the RC Channel axle and some custom rims should be about right. You just can’t use the tamiya super single rims with the hex drive from the refrigerated trailer they will still be to wide.
This is just how I do it, so experiment and find what works for you there is not a wrong or right way as long as it works and you’re happy