I'll be keeping an eye on this as your ideas progress Gerry. See what nice ideas you come up with.
The two spindle concept has plenty of merit IMO.
I don't believe running one rail per spindle will be a problem if done right.
I see by your pics that the spindle center line can go even closer to the rail which would be desirable. The closer the better.
I do however think you will need to mount the rails on something better than wood.
They only have a 20mm wide mounting surface. An aluminium (Aussie spelling ) plate would fit the bill nicely there.