I'm trying to create my first "homes" for mason bees, and I'm wondering how deep the holes need to be. I've bought some untreated 4X5 inch pine from Home Depot, and I could either drill into the 5" side or the 4" side. Somewhere I read that the holes should be 5/16" x 5" deep, but that would necessitate some fancy drilling, since my drillbit only goes 4" deep. Does anyone know if 4" holes would be sufficient? Obvious complete newbie here, any help greatly appreciated.