Jazzcnc - thanks for your comments, I was planning on using the proper profile jointing bolts with the angle for support. If that makes a difference? I did think that using 12mm plate was a little thin. So I'll redesign with the 20mm that eddiecurrent suggests. I'll have another think for the gantry too.

Eddiecurrent - thankyou also for your input. I'll have another look at the gantry. The X ballscrews were put there for convenience to attach to the profile. If there are benefits to having them level then I'll definately lift them. Thanks for the site link too.

Finding this forum has already probably saved me a fortune in redesigns, I appreciate the help im getting.