Affordable Oxygen

I was given an older MH EDS unit to install in my Phoebus glider which I got for a song and am restoring. The glider has a bracket for the oxygen tank, but no tank is installed. The bottom is a rounded fiberglass cup, and there is a flip bracket to go around the neck. It sits behind the seat pan to the right of the landing gear. The cup measures about 5 1/2" inside diameter, but the felt strip padding inside reduces that somewhat by up to 1/4" or so. The neck bracket is about 16" from where the curve of the bottom cup starts. I THINK (but am not sure) a MH AL647 tank will fit, but it has a flat bottom and I'm not sure how much I far forward I can get the tank in the neck bracket so it will fit, as this tank measures 16 1/2", according the the chart on W&W site. Plus, the tank and a plain regulator will run almost 1/4 the cost of what I paid for the glider. I'm pretty sure I can get a plain D-cylinder to fit, as it is narrower and could fit deeper into the curved cup for the bottom of the tank.

This has gotten me thinking then: is there any reason one couldn't use a standard "yolk-style" primary regulator for the oxygen tank? It would be much more affordable, and easier for me to get one of these style tanks, as I work in the medical field.