My guess is TD's were designed using Raichles/Deeluxe boots. When I changed over to UPZ boots from Deeluxe I had to change the toe/heel blocks postions on my TD3's more inwards so it is a pain to adjust angles as the heel and toe blocks ended up over or blocking the center mounting screw heads and need to be loosened or removed to adjust angles.
"TD3 2nd Board Kit
The 2nd board kit is everything you need to mount a second board and not have to worry about stance width everytime. Comes with 2 disks of your choice, e-rings of your choice, center disks of your choice, and the M6 screws to mount everything."
https://www.bomberonline.com/TD3-2nd-Board-Kit_p_26.html