Adjusting Linn Keltiks

I have Linn Keltiks with 4 Klouts.
Have struggled for a long time to adjust the bass. Don't get me wrong - they are superb speakers and sound wonderful but I find it is very difficult to achieve a balance between bass that is too light and bass that booms slightly. The real problem with the boom is not knowing whether it is a room resonance (the room is large - about 23ft square - but one speaker has to be nearer a corner than the other), whether it is due to distance from the wall, or whether it can be cured by adjusting the cards, or whether it is caused by a combination of all these!
Have tried to adjust the Aktiv cards and have ended up with bass settings Extension 1+2 (30Hz) and Level 1 (slightly too light) and Extension 1+2+3 (20Hz) and Level 1 (slightly too heavy). Then there is the distance from the wall which is also difficult to adjust (too near - imaging suffers, too far - domestically unacceptable).
Has anyone else any experience of adjusting Keltiks?
Regards
Brian