!!!!!!!!!!!! Now that makes my mouth water!!!!!! The last picture of thouse cylinders!!!!!!!!!!
How about just using solid stock for the rails? Then you don't have to worry about a collapsed bend. It's a pain in the butt, but for bending these small diameter tubes in ss and brass I've found it easier to make my own concave bending wheels. There are a lot of hand benders and nice tools but few of them bend a tight radius our modes need without having a pile of "spare" parts
. And the more I look at it the more I have to say the undercarriage on your machines are outstanding!!