Gonna place an order VERY soon! I also have plenty of 0.25" MDF stocked, and will be using that lasercut, along with wooden half-balls, for the robot. Benefit to MDF is the ease of lasercutting and its low density. The biggest risk in using MDF is its low stiffness, as it only has a E of 4GPa, but it can probably work with some additional Aluminum parts. Making sure the clamping mechanism doesn't yield the machine will be one of the most important parts of the design moving forward.