Thanks John, Col, Simon
Alistair, just checked the weight on mums kitchen scales and it comes up to 2.3kg's (thats just the bare frame as seen in the pics) I'm not really worried about keeping the weight down as this is going to go on my horse shoe mount on which weight isn't an issue.
You would have a heart attack if you knew how I'm mounting the primary, so I won't mention it just yet
Thanks for your help Ken, Simon, and Alistair regarding the secondary size, 70mm she is
I got a little bit more done on the secondary holder this arvo after school, here is a few pics.
Cheers
Jo