What % would be normal for mated queens compared to cells placed in nucs?
There are too many factors involved and it changes continuously. Weather plays a big part in it. At times I have almost 100% and at other times I have had as low as 50% or less. I guess I would figure 75-80% to play it safe. If you have a few left over, you can make a few more nucs or find someone to take them off your hands.
I am trying to build up my hive numbers and hate to do splits and then not have queen to put in them.
I hear you, and like your idea. I'm not one for making walk away splits. Your better off to rear your own quality queens and then make your splits with them.
Robo, I built a copy of your bee vac and it worked great.
Excellent, glad it is working out for you. I've had great luck with mine and I have gotten a lot of positive feedback from other folks that have built them.