A 350 X-over to the RD75 would be excellent. You don't think that will be any issue in terms of obstructing the output from the woofer-array up to 350?

10" will be to wide I'm afraid, there's some serious WAF restrictions on the width (height and depth are less critical) of the speaker. That's also the reason why I want the mid/tweet in front of the woofers - I would certainly place it besides the woofer-line if possible.

8-inchers may work though. I have been looking av 8 Peerless SLS-8 (830667) per side, also a nicely priced alternative with a healthy 13mm P-P excursion. This would allow for a full-range, skipping the subs altogether. Could be a good idea...

Regarding the choice of tweeter/mid I can't see that I have a choice for this design. Going with an array of smaller units (like the Neo8) will not allow a cross at 350 without serious compromises i SQ. A long and robust ribbon could do the trick, but short of DIYing one (which I don't dear attempt) they seem to be in short supply... Do you have any suggestions?