Pendulum uses a 20mm thick plate of toolox that is then watercut for the beater, with the ends turned to spin inside bearings. id say 20mm thickness its minimum, 250mm dia 300mm length is very big though, mines 145mm dia and 240mm side for comparison. Id avoid using multiple parts to make the beater weapon since itll just cause more weak points, id say 25mm thickness is safe if you do go with the size you want.