Clio, thank you very much for the two links. I've found the first link myself but did not find the explanations very clear. The second link you sent me gives a better description of the procedure (IMO). I will study the procedure closely and give it a try next week.
Spaz, it is unfortunate that you are unable to move the speakers against a different wall. If the speakers are indeed position against the "wrong" wall you may never be able to get decent bass in your room. Even if you would add a subwoofer (2 might solve the problem but one can never be sure)! As mentioned in my first post, the bass was almost inexistent in my room even though the volume of my REL was half way up (this was for the arrangement depicted in the plan shown on my system page). I have place the speakers against all 4 walls and the amount and quality of the bass varied very significantly from one configuration to another, i.e. from inexistent to too much (when the speakers where placed against the short wall), and from decent to very good (when the speakers were against the long wall).
Regarding your question about the ceiling, fake walls never count. Consequently, your room is larger. It is hard to say whether or not this is causing the lack of bass you currently experience. However, I would say that your speaker are large enough to not get lost in in your room (they should be able to move enough air).
Finally, do you get more bass if you play the music at larger volumes?