Hi Pierre

This is exactly what I did on my build (see my build here post #10) . My Gantry is 700mm wide so I think I spaced them at between 120 - 150 mm apart, drilled through the profile so I could tighten the bolts. I was using much heavier material than you are (4 kg/m) and only 80 x 40 profile. The L shape inspired by Jazz gives great resistance to torsion. What type of spindle will you be using? The spindle I have weighs over 2kg hence the use of the heavy gauge profile to resist torsion. I have some concerns about the thickness of the material you are using for your gantry if you have a heavy spindle plus the weight of your Z axis ballscrew, bearings and stepper/servo motor?

Kind Regards
Michael