Hi Steve,
I like your clear drawings, but the drawing of the scope makes the pier and mount look pretty small - maybe it's just the perspective. Do you know how heavy your scope and mount will be?
I am thinking that you might want (or need) to beef-up the pipe diameter a little. I used a very similar design with 250 mm bolt spacing on the square plates and found that I needed to use 19 mm bolts (actually threaded rod) rather than 12 mm which resulted in too much flex with my set up. Each threaded rod was 250 mm long, and I had a 8" SCT on a wedge. This arrangement provides a steady platform.
http://www.iceinspace.com.au/forum/a...se.php?a=76330
Chris