That’s really cool!
If you are ever looking for a slightly more efficient way to join two shafts together end-to-end, there’s a new VEX IQ part (228-2500-1925) that was created a few years ago for use in the HEXBUG VEX Robotics kits. This part is similar to the 2x2 Lock Plate, but the square hole is offset by one beam thickness (with enough room to fit a Rubber Shaft Collar), and the outside is round.
Currently, the part is only available in limited quantities in a few of these kits, such as
1x here in Orange: HEXBUG Micro Robotic Creatures | HEXBUG
2x here in Light Grey: HEXBUG Micro Robotic Creatures | HEXBUG
3x here in Crimson Red: HEXBUG Micro Robotic Creatures | HEXBUG
And a few other kits, such as the Balancing Boxers and the Mech Loader model in the VEX Explorer kits.
We really like the usefulness of this part, and have been trying to increase our usage of it in new kits where ever possible.