egg trays

[R/R farm]

hello, to all. I have recently starting working on a homemade incubator of my own. I went with the sportsman style incubator with a few changes. I have a hatching tray in the bottom. My question is how far apart should the egg trays be from each other. My egg trays dont rotate as i prefer to turn the eggs myself. Each tray slides out like a drawer. I have a couple trays built so far. Just wondering , How close is too close?, How far apart would be best? Thanks for any help. Hope to get some pics on soon.