In the most recent three wheels sets I built, I used 2oz of Stan's in each wheel. The wheels were Iplay 30mm hookless 29ers with Racing Ralph tires. Of the six wheels, only one had even the slightest trouble sealing. Five wheels sealed immediately and have been fine for a month now with a couple hundred miles. The odd wheel out simple required pumping it up three times and shaking the fluid around. Now it is fine and holding perfectly.
One wheel got a pretty nasty sidewall puncture on it's first ride out, resulting in a ~1/8th" hole. The sealant was able to seal the hole after some work. First I took the wheel off and placed the hole down so that the sealant could pool above the hole. After it squirted for a bit and plugged up, I added a bit of air. It started to bubble again so I let the pool sit over the hole again. I repeated this three or four times until the tire was up to about 20 psi and the hole wasn't leaking. We rode another 10 miles to get back to the cars without trouble. We later patched the inside casing with a tube patch and it has been holding perfectly since then.
I think when you are not using "Tubeless Ready" tires, you will need additional sealant to get the system to hold pressure. My Giant with non-tubeless rims and non-tubeless ready tires took quite a bit of sealant the first time. Now I refill the wheels with 2oz ever few months. Which leads me to me next point...
DON'T FORGET TO REFILL YOUR WHEELS WITH SEALANT PERIODICALLY! Out here in AZ, I refill my wheels every 4 to 6 months because the heat seems to dry them out quickly. There is nothing worse than dropping out of a race or ride because of a flat because you forgot to rejuice your wheels.