I find my Irvin jacket with heater keeping legs warm more than enough. It's bulk is acceptable without passenger. I remember when flying Piper Arrow that I couldn't quite align with control column due to thickness of jacket against left side of cabin, though not an issue otherwise.
We have three setting heated seats in the Mini but find them pointless for other than taking away cold soak when car left outside. No way can I leave them on even with coolest setting.
.
