Took me a while to get back to this, I was out of town for work. Anyway, yesterday, I ordered a 1/2" collet from Hitachi. Since it's a brand new collet, my guess is however snug of a fit this collet has, that is the "right" fit ("right" amount of friction on the bit).
I have to admit, Hitachi's customer is quite good. This is the second time I had to order a part from them and they sent the parts for free (even free shipping). Then again, I really haven't talked to customer service for any of my woodworking tools in the past, so I don't have a benchmark.