i thought i would update everyone on the build plates.
we have been experimenting with magnetic bottoms with great success.
we simply purchased some 1mm stickyback magnetic sheet and adhered it to the bottom of the build plate and purchased some stickyback
ferras paper and adhered it to the top of the bed.
the result is it pulls the plate to the bed perfectly and comes off easily, i think this will solve the issue with the larger plates slightly warping in the middle where no clamps can help.
i now have no need for clamps

the downside is it makes the build plate 1mm thicker, but we think the best way would be to use 2mm acrylic instead of 3mm to overcome that problem.

with the issue of the build plate material unsticking and sometimes bubbling we have decided to us 3m double sided sticky sheets between the layers and that seems to make the top layer adhere much better and should overcome any bubbling.

any thoughts!