Your choice of two types of nylons to have your rails build from. The more expensive type has higher stiffness and dimensional stability.
Contact Tom Luque if you would like to make your own metal cast using low temp plastic (PLA).
Built for 1973 C&C 25 sailboat.
Uses two 4-40 x 3/8 for mounting and allen key 3/32" size.
Drill holes with #34 bit and tap with 4-40
Use marine type anti-seize on threads to prevent corrosion.
Version; pg353A profile H1 v.6