Picatinny. Solid, secure, standard dimensions.
GG&G makes one that has all the bugs worked out. It's solid, bullet proof (hard anodized), *standard* dimensions, and doesn't just grip the rail lips (most of which end up sliding, in my experience), but drives the set screw into the back of the t-slot fore-end rail.
They also make a bipod adapter - originally meant for attaching a Harris bipod (sling swivel stud mount) to a picatinny rail. Again, it is solid, well-engineered, and pretty much bullet proof. Plus it interfaces nicely with the above rail adapter - or any other rail section people might use.
John Weil, who made the CenterShot Bipods for a while, used these adapters on his bipods. They removed the sling stud, drilled and counter-bored two holes for attaching to the bipod top, and called it a day. Rock-freaking-solid. Never slips, never budges. Comes off easily with the flip of a QD lever. The cam angles are well thought out, and already debugged for ya.
The only real downsides... probably a little more heavy duty than something designed for F-class only. Definitely not cheap - not hideously expensive, but maybe buying bulk you could get a break on the pricing. And they come in one color - flat anodized black.
I love my Seb JoyPod, but this is one area I would recommend not doing what they did - making their own rail adapter and clamp. The new ones are better than the original, but the GG&G are still better.
Don't reinvent the wheel.
