hi PuppyWoofie

There is a spreadsheet on the site somewhere, sorry cant recall the link to it, which allows you to enter various materials and sizes and works out the amount of "flex" you can expect to see. It will of course depend on what you are going to do with it as to if that extrusion will be suitable.

My gantry is about the same length but I decided I needed something stronger than extrusion for the materials I want to work. I also seem to recall that reinforcing the extrusion was a viable option. Have a dig around with the search tool, I'm sure I've seen that question discussed before.