Hi Peter,
Just lost my reply to you - try again.
".......... the temp advantage, despite the less than expected delta, makes a difference. "
Agree! My airbox was delivering ambient temperature air to the carbs (see below). My current minimalist cone air filters are delivering ambient + 15C+ air. There is a noticeable difference in engine performance. Was gettin 147 knots indicated at WOT - now only 140 knots.
"...........better engine performance (and climb) during winter times."
Absolutely! My Sonex took on turbo prop characteristics this past winter😁. Strangely my ATEC Zephyr/912ULS did not have such a dramatic winter performance improvement.
"..........find a way to mount the airbox in a way that it supports the carbs.."
Certainly explore this. Support must move with engine. Previous speculation (firewall mount) won't do.