The #6 crossing needs $6 turnouts to come out square. With #8s, the turnouts will lean in towards one another as you move away from the crossing. I just drew it quick in 3rdPlanIt. To make it work with #8s, you's need to add some straight track to the 4 legs of the crossing, the at the point end of each of the 4 turnouts, you'd have to put in some curves to get the two tracks parallel again. If you mean just 2 turnouts, so there are 3 tracks, with the turnouts there to allow a train to move from track 1 to track 3, crossing over track 2, if you do that with #8s, then you will need curves on the point ends of the turnouts to bring them parallel with the center track.
One of the things I am not doing is making double crossovers - I am building thm up out of 4 turnouts and just having one cross from track 1 to track 2, then a follow up one cross from track 2 back to track 1. One reason is - Peco doesn't have a crossing that matches #8 turnouts.
--Randy
