This is my modified clamp showing the re-tapped center hole with a 3/8 stud.
I use a pan / tilt head on it, this is an ebay cheap s*** thing, but it's aluminium, light, takes my Manfrotto QR plates and is smooth and rock solid. I don't use it everyday, it's perfectly good.
The flexible neck is a good addition, this is a heavy(ish) old S1a and it will hold this without a great deal of problem. It'll hold my NEX or a flash with no problem. It wont hold my K10, battery pack and 50-135! . Tapping the center hole doesn't affect this mount at all.
I also drilled and tapped the end, it's not soomething I use a lot but it has made life easier on odd occassions.
Re-tapping the center hole will obviously alter the original design and the way it works with other accessories designed to fit in the original threaded hole, but I have a few of these and this is actually the only one I use.
Forgive the crappy pictures, I had to use a very old Canon compact as my batteries are on charge in everything else.