Hi Graham,
Apologies for bombarding you with questions, again, some of which you must be thinking hmmm....

Your theoretical descriptions of OB speaker science are extremely insightful and just maybe there are a few other DIY newbies out there like me who are learning a lot from them. I suspected this multi-speaker project might be somewhat ambitious, however, even where I'm at now, I'm not too far away from getting a very nice sounding speaker. I shall plug away at it.
Not sure why I questioned the B200 height on your Spirit Mk11s as a I agree with you about hearing vocals projected from 'a reasonably correct' height. Maybe as they are tall enough to generate this at 'standing' as well as sitting heights. At listening sessions at friends who have much higher end systems than mine, I occasionally find myself sitting on the floor to get tweeters positioned a little above ear height for exactly this reason. My current test baffle however sounds best sitting at normal chair height, as I hear more of the Saba 20 cm positioned at the top which is assisting the lower mids of the B200, and as the tweeter is only a little above ear height. So I'm contented here.
I hope you're well and thanks again for your help.
cheers.. jeffac