Spacing is the critical answer when making your own slatted racks. That's why I advised Zoot, and others who have made my design of a slatted rack, to use 1 inch doweling. I hate plastic in a bee hive, call me old fashioned, but I prefer wood and when it comes to wood, cedar when I can find it and afford it. For proper spacing and demensions on racks always refer to the width of the top bar of your frames--a smidgin wider is necessary.