I ran into a design problem after getting the carriages done. I assembled the two carriages to the gantry tube and placed the assembly on the base. Something didn't look right. I took a measurement from the base to the gantry tube and only had 4.5" on clearance. My cad model showed 6.5". After digging into it, I figured out that my cad model for the sides was incorrect. To fix it, I glued two pieces of 3/4" birch veneer plywood together and cut them out to the proper dimensions. I then sandwiched the plywood between the aluminum sides and the base. I added some lag bolts that go through the aluminum sides and into the plywood.