Friendly C4 shouldn't stick to the internal surfaces of allied vehicles, because there are some people out there who try to increase the lethality of explosives with "accidental" C4 being strapped to the inside of helicopters/boats etc. —as any detonations to enemy explosives count as your kill.
There are people who use this as a method of Griefing and will spread the action out to their friends, which makes banning them to mitigate this, that much harder.
External surfaces/collision boxes would remain sticky, so your Quadbike C4 strategies are still viable.
Griefing is toxic and petty, and should not be endorsed in any manner.
revised
this is about vehicles and c4
fuck it im down with that