I heard a bout an issue but more torque at the bottom the of neck, although I’m unsure if this was more for the freestyle side or the trials side of it. Both have different stresses on the frame. Any body hear anymore about this?
Longneck adds the same amount of pressure as a smaller frame, given the seats are at the same height. The only difference is that with a shortneck, more of the seat posts acts like a lever, and in a longneck it’s the frame. Same end result.
Longneck all the way. If it’s a little too long you can cut it, that is what I did to a koxx freestyle frame. It keeps the clamp out of the way, which is nice. Short of being a midget, or for some unfathomable reason enjoying your seat the height of a shortneck frame get a longneck. Looks better, and saves same weight, at least with a kh if your running a steel post, maybe alu, but I don’t know. If you like your seat slammed in a longneck, you can run a stump post, which is a lot lighter than having a huge post. Even if not slammed, you can cut your post way shorter than you can with a shortneck.
The point is that the frame is thicker than the seat post, so probably stronger. At least I’ve never heard of a KH longneck frame that didn’t break at the crown… If you have a longneck nimbus steel frame, you can bet that it won’t be a problem.
I’ve been riding a KH longneck for a a year and a half, and haven’t changed my tryall reinforced seatpost (yeah the ones that are like cheese…). I still don’t know wether I got a really good one, or wether the longneck really gives alot less stress on it. Maybe I’m just super smooth… 
Excuse me, but don’t all kh frames break at the crown? I don’t see what your saying as relevant.
I’ve never seen a frame break above the crown, and I’m guessing a steal seatpost is as strong as, or stronger than an alu frame, though the strength is completely an irrelevant issue when talking about the leverage put onto the crown.
A long neck will produce the same stress as a short neck with the same seat height. Period, the effective lever, no matter what is is made of, is the same length. The crown doesn’t know whether the lever is made up of frame or seat post.
Why would a long neck stress a seat post more or less? Unless the seat post was malformed part way down near the middle of the post in a shortneck, and running a longneck would allow it to be slammed, avoided this problem area part way down. Again, I’ve never seat a seat post break like this, as I’ve never seen a frame break like this, mid tubing.
I think your over thinking the issue. I can assure you, they produce the same force on the crown, given kh longnecks are just shortnecks with a longer tube.