HICTOP build plate leveler

Like most people, my build plate on my HICTOP 3DP-11-AL (3DP-12) was fairly badly bowed down in the middle and was a little worse in the front than in the back. This results in pretty poor 'auto-leveling' using the inductive sensor. Updating firmware to include bilinear (mesh) leveling helped some, but the bowing effect could still be observed. I designed this piece to sit underneath the build plate on the carriage, and push up just slightly to minimize bowing. The smaller pieces are just twiste