If you're to the point where you need a flatter wake then you need to be looking at tournament style direct drives, or possibly a V-drive as a halfway house.
Sportsboats and mellow flat wakes just don't go hand in hand I'm afraid. Its just something you'll need to live with. I can run a 6-buoy course ont he stick, but when behind my 1800SR maxum I just have to accept that the wakes going to beat me up a bit... if anything it makes it a little more fun... and at the end of the day... there's no way you should be putting a Maxum through the slalom course so it doesn't really make any odds either way.
Just ski for the fun and if you want to take it further then go to a ski club
A different ski might help too... what are you riding now? One things for sure... you'll be wasting you're time if you went out and bought something like an O'Brien Siege or Mapple.