Using Proto48 with On30 WILL give you the correct spacing for what we are accustomed to seeing in the world of 3ft/standard gauge track with the narrow gauge rail being closer top the outside rail. The drawback is building a correct Proto48 standard gauge loco. On our layout we used a Bachmann/Williams Ge44 tonner converted to Proto48 using NWSL Stanton drives. Works great and makes a seet running loco.