The offside wing gets very hot over the cat, and in fact the underseal goes shiny and wet when the cat is hot. So I played around with some offcuts of aluminium, and some woven heat barrier, and some 'Reflect-a-Cool' and this is what happened:
A simple rectangle, approx 8" x 9" bent over the cat.

With Reflect a Cool on the outside.

Woven mat on the inside:

Securing legs bolted on and insulated:

The cat with a lick of high temp paint where it shows.

It works well, but the wing still gets warm, so I may try spacing the shield a bit further from the cat surface.