JAZZCNC, if you read this I have a question for you. How do you go about assembling the L-shape gantry together? I have received my aluminium profiles and to my surprise I noticed that they are not flat in the middle. It is probably hard to see in the picture but it is about 0.5mm.

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I was thinking that I could sand it down, since the only critical thing would be that it is flat on the sides so that it wont wiggle when assembled.