Missed on this combo?

I'll give my extremely limited experience with Hughes. I bought their small block roller rockers and they were excellent so far I like them a lot. BUT- when I called to ask why they're studs in my heads and when I tighten there nut all the way down I still have a quarter inch gap before the rocker shaft touches the top of the head? And they said if everything's tight then it's all good to run? But I'm telling you there's that quarter inch space between the bottom of the shaft and the head? anyways I thanked them for their help and had to stack some washers between the spacer and the nut to make sure the shafts held down against the head. They were kind, answered all my questions but we're actually no help figuring it out...