Thanks for the feedback everyone - I have been trying to reply but I think because I only just joined my messages are sitting waiting for moderator approval.

JAZZCNC - that model you have done is pretty much spot on what I am after, just the pillars need to come flush with the outer sides, and be a bit smaller in diameter. Would you be able to make a sample for me? I need to check the fitment with the bag manufacturer, if they give it the ok then I'd be ready to order the 20 to start (obviously price permitting, if you can give a rough quote that would be very helpful - I know they won't fall into the 'cheap' category, but the lower the better :) ).