I have been building telescopes since 1960, including two 8 in Springfields and a 12.5 in f6.25 modular (and actually portable) Springfield. I have accepted that the first
diagonal mirror must be a little larger. Materials include everything from heavy machined steel and bronze to teflon and poor man's carbon fiber (plywood). Viewing comfort
is excellent, like sitting at a desk with a microscope while the telescope points anywhere in the sky. Optical performance has been superb, but it is important that everything be orthogonal so that the optical and mechanical axes are co-linear. Built the first Springfield in 1962. Now building what may be my last, a 17.5 incher, f4.45 with a secondary minor axis of 4.8 inches. With two diagonal mirrors I believe each must be 20th wave or better, since the wavefront error will be additive. Keep as much of the cone of light inside
the main tube as you can, but you have to allow for the the height of your head above the level of your pupils in order to comfortably get you eye over the ocular. Hurray for the Springfield Telescope Makers and Russel porter!

Very interesting and a telescope I would like to look through one day.

As an old person with a bad back, I love my 6" f8 Springsonian mounted on a Dob mount. I did not make it; a member of the Rose City Astronomers in Portland, Oregon did that. I could provide pictures if desired.

Hi Bruce,
I would love to see some pics of how it was done on your Dob. I am currently working on an 8"F7.5 an am debating whether I could do it on a Springfield mount.. It would likely be going onto an AZ GOTO mount - hence my interest in yours.
Cheers - Malcolm