Your mixing scale and gauge. O gauge isn't really correctly scaled for 1:48 first off. So any comparisons of scale is redundant.
Ho gauge is very close to half of O gauge.
So close you can in fact sometimes run an HO engine on the center rail and one outer rail of some 3r O track.
Ive done it.
Curves weren't real great but fwd/ rev was no issue (tube track and scalish ho flanges and it still worked, lol) Something like GG or other T profile 3r track might work like a charm for HO too.(except for turnouts, etc 
)
