I don't expect it would stain the carpet but the carpet itself esp. covered can give the little shits a place to hide.

True, light cycle is MOST important in flower... since you are flowering soon anyway, why not time it to coincide, or start flowering a couple days earlier? Or you could just not worry too much, lol.. Personally I wou;dn't sweat it.
Oh did you get my rep message? I sent you contact info