Mainline through the double-slip turnouts. I have been concerned about this myself. Did a search and did not find concerns about these Atlas turnouts. But perhaps I have missed these issues?
I may have gotten complacent after using the nearly bullet-proof FasTrack turnouts.
The double-slips save so much darned space they are tempting. Perhaps I should look at using Ross/Gargraves. Ross has #4 turnouts that will save some space. As they say if football "Its a game of inches".