Thanks for the info. The deflection was calculated only for one 100x50 5mm box section as in my first design, now there are 2 in an L shape.
This is meant to be a hobby machine so I honestly dont know how much aluminium will be cut on it but I do know I want to be able to cut so I will take the advice and modify the x sides to bring the y axis down.
Has anyone ever built the gantry with the carriages in a triangle formation? I am thinking if the 2 bottom cariages were 150mm apart and the top 2 were 250mm apart (from outside dimension) I could keep the same footprint and machining area?
Cheers, Charlie