Where are the good CDs?

I'm level 17 and I browse the transfer market every few hours for CDs with a big 4 strength and cooling/reliability weakness and found none. My current one is downforce strength and tyre economy weakness but that's just one of the few I've found, others were pretty much the same as mine and had loads bidding on it. I know that there's a lot of people who store good CDs in their other teams that aren't in leagues sand i think that there should be a limit of 2 or 3 CDs in a team that isn't in a league, that could be a good solution. Or iGP could generate a ton of good CDs(Level 15+) and put them on the transfer market.