The four way crossover causes a 10.5" track center to center as you've discovered. You can leave out the 1 3/8" on the turnout to the 45 cross. Then you trim the roadbed on the cross to make them fit like the half-roadbed pieces. That gets you a 9 inch center to center. Don't get married to it. It causes awkward fits as you found, also. It looks cool. I use it on my layout, but I was able to make up the 3" difference in the center rail spacing on the inside line at 90° corners of the inner track at both ends.
Keeping close to the 6" center to center spacing of FasTrack will use less track.
