This is just me, but I would do the opposite, use the rails, not the foam. The foam takes up too much room. Just put the rails in the slot closest to the eggs without touching. They won't crack with just a little space between the rail and the eggCandling results are great. I have 8 eggs which are questionable; 4 might be red rings, 4 might be clears...so assuming they are what I worry they are, I'm looking at a 90.48% hatch rate...hopefully no lower than that.
As for the rails, yeah, definitely not going to use them again. I will just use foam strips between the eggs next time. I don't usually use X-Large eggs in the bator, but this time I did have to use some to fill it up...and they were kinda clumped together...so again, my fault not really Brinsea's.