Did you find a trailer?
I want to tote our two Border Collie fur-babies (~90lbs). I'm not having a great time locating my ideal trailer. Moto-mule comes closest and cheapest.
If I custom-made my own:
Attachment Point: I don't want a rough ride so I would like to attach it to the sub-frame to soak up impacts.
Frame & Box: I'd want a roll-cage with some kind of padding to reduce injuries for unpredictable situations. For wind and debris protection, maybe Lexan with some 3M film to prevent chips on the front and block UV but still be see-through. Mesh on the sides and more Lexan on the back to prevent fumes from being sucked into their cabin.
Wheel & Swingarm: I'm thinking a rear-end off an Apollo 125 dirt-bike as they seem to be cheap/common enough. I could maybe use the headtube for the pivot point.
Braking: Since I have the DCT, I'd get a left-hand brake and run a hose terminated with a drybreak non-spill coupling connector to the tail to connect with the hose to the trailer's caliper.
The main issue I can think of is if the dogs shift their weight and affect rotational/twist force or tongue weight, whether driving straight or in a corner. This makes me lean towards a wagon trailer, which affects cost, weight, and/or complexity...but solves the rotational/tongue-weight-shifting issue. Also, it could then be attached to the rear axle, but the trailer steering would be thrown off after hitting a bump mid-turn either way...
Maybe I should just go with the Wallick leaning dual side-car approach...If I had many, many more thousands of discretionary dollars...and it probably has its own issues with fore-aft weight shifting forces. Meh, I'm stuck with a car or a motorcycle and no bundles of joy. I wouldn't ride a non-leaning motorcycle.