Why are you guys using seat heat mats that require relays (with attendant weight and complexity concern)? There are trim-able carbon heat elements in the auto aftermarket world that have Hi-Lo switches but no relays required. I had a set for the RV-6A before the house fire
that I never had a chance to install and enjoy. The wiring harness was not particularly heavy. Switches look exactly like those pictured in this thread.
They were procured a long time ago and I don't have a source or part # anymore.
For future reference I'd like to know the perceived advantages of the heaters you are discussing here, vs. what I had.
-Bill B