I have a Zipp 808 wheel that requires a long valve (92mm). I would really like to find a tube that has the required length valve without having to piece together an extender. Zipp did not know of a one-piece valve that was available for this wheel. I have heard it is better to get an extender with a "removable valve core" to ensure a tight fit with no leaks. Why is the removable core valve a better choice?

If anyone knows where I can get a tube with a 92mm valve without having to piece it together please advise... or if you know of a foolproof way to use an extender without worrying about leaking also please let me know. The last thing I want is to be fixing a flat on the side of the road during a race and having to worry about a valve extender...

And... the million dollar question... why doesn't anyone make these as one piece??