I can't speak to the prop desk issue, but one good thing about Advantage is that the CME lists them on their website as a clearing firm for all 4 major divisions - meaning there shouldn't be a behind-the-scenes omnibus clearing agreement through someone else. This is apparently where several non-MF traders got in trouble - because their clearing firm was not a direct exchange clearing firm, but cleared through MF. So they were barred from trading until it all got sorted out.