Joe,
I don't know. I have no experience with standard gauge. You improve you overhang problem by increasing the radii, however the distance between track centers drops from 8.5" to 6". If this was all O scale then that would not be a problem as 4.5" spacing would suffice.
If standard gauge trains are fine with std57 and std72 curves (7.5" spacing) then I would feel confident that your initial plan would work and possibly this lastest plan.
I would follow Bob's suggestion.
Jan.