Mounting a Series 3 in a Rotisserie

1973, Series 3, FHC;

After a long wait, I'm finally at work on this project. The engine and the back axle are both out.

I bought a rotisserie and I’m wondering how to attach it.
The front is easy. There are enough existing holes in the frame with the engine removed to bolt too.

But the boot is just thin sheet metal. There’s nothing substantial enough to bolt too which will bear the weight of the body shell when inverted. I could build a big angle-iron structure that transfers the forces to rear rear axle box, but that seems like overkill.

Have you ever seen this done? Do you know anyone who’s done it?
Any guidance would be much appreciated.

Thanks
Neil C