I've been wondering the same thing. My crew cab is getting a Cummins 4x4 swap, and I'd like it to sit as high as a new one.

Flipping the shackle completely changes the dynamic and static loads it was designed for. It's now experiencing compression loads instead of tension, and everyone should know that metals are stronger in tension than compression. The added detractor is that the ability to deal with side loads is greatly diminished, simply because of the architecture. I plan on using custom springs to get the height I want and keep the shackles in tension.

I don't think towing a small load like a car and trailer would be too bad as long as you don't drive very fast and keep any sway under control. Make sure to keep the trailer's CG and tongue weight in check, too.