-Dan
Builder of Bowser steam! Railimages Site
You can gap the 'away' rails of a powered frog turnout anywhere out to the clearance point (the point at which rolling stock on the converging tracks would sideswipe.) Placing the gap farther away could lead to electrical shorts as a locomotive pulls up to hold in the clear of a turnout set to the opposite route.
OTOH, if the turnout leads to a stub-end siding, no gap is necessary unless you want to park a sound-equipped loco on the spur and keep the sound running.
Chuck (modeling Central Japan in September, 1964 - with hand-laid specialwork)