if the water in your qt tank is stable and easily maintained, i would see no reason why not, you could easily keep a pair in a 10 or 20 gallon for a couple of days(20 or so), but if it is a 20, i would not kep them in there for months, but if you need to q them later on they are gonna need to be in the tank together anyway,
i would, i woudl just make sure to get a runt, just to make sure it is a male, the one you have, you have no idea for sure, but 2 males, one will switch, but 2 females may be trouble, there are no guarentees ever, but your odds, ifeel, will be better and q-ing them together would make it easier to catch one in an empty q tank if need be than in your show tank
back to your q' you have had your clown in the q for 3 wks. so things should be pretty stable by now, and although i do not recc. going fast, they are not going into your main tank, so you are not risking your tank with disease or anything, but i would ot make it a practice to add fish to your q all the time, while other fish are q-ing