Hey Tommy, yer points are quite correct but don't think George is trying to put words in your mouth, opinions are like ar se holes, every cants got one and we respect yours so dont disrespect others.
No pictures Colin but what I remember is you run a pipe ( plastic 6-8 inch )the full length of the loft inside at the highest point.It has holes cut in it from small to large creating a draw of air. Maybe someone else on here knows more about the system and could post it up.
I agree that ye need plenty young birds about you when starting out to be left with enough to fly as obs but for me you should keep them in a big loft if possible. Steven Van Breemens space age ventilation system can help ye keep a lot of birds in a small loft.