Thanks Jazzcnc for taking the time to review this. The photos are really useful. My drawings are incomplete at this stage as I will be using a single ballscrew on the long axis as per your photo with a plate underneath between the gantry sides . But the tip on adding the extra reinforcement on the long axis is taken and accepted. HiltonSteve's router/mill also had this. It also solves the problem of mounting the BF/BK blocks very elegantly and protects the ballscrew from muck! Many thanks!!

Again the comment on the material thickness on the Z axis is accepted and you given me some food for thought on the gantry side plate lay back. My original idea is to get the cg of the Z axis between the bearings on the side plate, but as you say well, cost of getting the plate for the gantry sides has to be taken into account!

I note your comment about reversing the position of the Z axis linear slides and bearings - I see in your photos you are using Hwin/THK slides which have better torque load characteristics than Supported round rail and linear slides. I'll have a think about that one.

Measure twice cut once is the adage!!!

Kind Regards
Mike