How would you do it?

[Old-tool-guy]

I think there are other designs that could work better, but the real problem is the amount of weight that you want to carry. You may have to fabricate something from scratch. This one has a better design and is 16" wide, but only a 60lb capacity.

Not sure i agree it’s a better design ... but it is a different design. The load is carried more vertically, which puts it closer to the bike but also raises the center of gravity. Either could work well, just have to evaluate the pros and cons and make a decision.