Paging Ernie L. - roller bender questions

Ernie,
I'm in the middle of building the roller tubing bender you designed and have shown on your web page.
One of the roller sets I want to build is for bending two inch round tubing
(although the queries I have apply equally to other sizes and shapes). Questions:
How big would I make the diameter of the half-round groove cut into the roller? I was thinking about adding .005", (IOW making the diameter 2.005"), but have no experience to go on. This is just my best guess. My other best guess is to make the diameter 2" assuming that the delrin will flex enough to let the roller fit properly.
I'm assuming the shape of the groove is "half-circular". I have a friend that looked at the drawings and thought the shape was elliptical - hence my question - but I assume what you did was make the shape of the groove match the tubing shape, i.e.: circular. Is this right?
While turning the rollers on my lathe, I was thinking of plunging a form cutter past its widest point by .250" or so. thereby creating a "wall"on either side of the groove in order to support the sides of the tubing and prevent them from bowing outward. Does this make sense?
If you have any suggestions or comments, please feel free to make them.
Thanks for the design and your help.
Regards,
Peter
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Make a cutter that is 2" diameter, and use that to cut the roller dies. The delrin will flex enough to conform to the tube.

Yes that is right. The tube shape has to match the die precisely, this way the tube is fully supported during rolling.

It is a good idea as long as you add steel side plates to the die to support the walls.

Sounds good so far.
There is a website that shows the hydraulic power variant of my roller. I just can't remember what is was
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Thank you!
Peter
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