I dont think people are actually gonna use that many trades in between rounds 3-11 as they have in the past. In fact im expecting far less otherwise your trading yourself to zero's which counteracts the points gained bu the upgrade in the first place.
So using 6 trades shouldnt be a worry as you should have plenty left coming into those rounds.
Im probably only looking at doing 4 upgrades to major premiums before the byes. Thats the way i see it right now.
Now I get ( with 3 trades thank god ).:
If you label them group 11, 12, 13.
Best result: round 11.
22 players , 8 in the bye. 8 group 11, 10 group 10, 12 group 13
Using 3 trades gives.
Round 12:
22 players, 8 in the bye. 11 group 11, 8 group 12 , 11 group 13.
Using 3 trades gives
Round 13: 11 group 11, 11 group 12, 8 group 13.
There are some different combinations, but to avoid any doughnuts it still involves every non bye player playing each game and using six trades.
Personally It will depend if there are trades there that I see value in making.