You're right it is short. But I specifically made like that for my brew day because I was only brewing a 2.5 gallon batch. Hence, the grain bill is also small...Anyway, I've made the proper adjustments in the design so that it can be adjusted.
Cute. The height of the cube is fixed, and doesn't account for differences in bag size, kettles, etc. They should have made it height-adjustable.
I think it would be easier to just build some kind of tripod device to attach a hoist. Maybe fashion it from an old camera tripod with adjustable legs so you can set the height exactly where you want it.