I make 6 foot long Planing Forms for Hex (6 sided) bamboo rodmaking.
I use a 5" Station Spacing setup for a total of 15 stations.
The groove tapers at approximately 0.001" per inch of length.
Each station consists of :
1) A precision 0.250" ground and hardened steel dowel to keep the two sides aligned in the same plane.
2) A 1/4" Socket Head Cap Screw (Allen screw) for the Pull screw with a custom brass Thrust Washer under the head.
3) A 1/4" Allen Set Screw for the Push screw.
The Tip side minimum station depths are from 0.020"-0.025 to 0.090"-0.095" approximately.
The Butt side minimum dimensions are 0.080" to 0.150" approx.
The Push and Pull screws are adjusted from opposite sides of the form. That way when you adjust the taper depth your hands are moving in the same direction at the same time.
I have recently started to add an etched and darkened logo to my Planing Forms.