I have a gen1 kit, shipped late 2018. Hot rod insulation instructions were separate, I have digital copy, revB from 2015.
http://www.factoryfiveparts.com/cont...insulation.pdf
Piece was rectangular. Here's a snapshot from those separate instructions.
insulation.jpg

Note in the instructions they say it's for the waterfall but this is where they show it in the pic.

Steve