Thanks very much, Roch222 and nu-be. I'll roll up my sleeves and give your suggestions a go. I'm not sure how to remove the shear... I know what it is, but I don't know where it is... but maybe I can find it. Also, I'll try some different camera angles and views.

It just seems strange that Peter's screenshots look identical to what I've got happening... and yet it's not working out. I can get the window cut out and the lights working nicely... but I still have levitating walls... ;)

Again... many thanks to both of you. I'm goin' back in...

:)