Originally Posted by PowerCell
You know, I've seen several people refer to 320mm front suspension. Originally Pyndon, and more recently Alex at Konflict. I'm not sure if they're transposing numbers or what, but the stock KTM EXC/SX forks run 300mm/302mm respectively. WP stuff is already a little edgy when it comes to overlap between the fork housing and the stanchion tubes (Íhlins complete forks run 24mm extra), so I can't recomend or even imagine pushing them another 20mm. The big bikes place a crap load of force on the fork slider bushings. To decrease that overlap even a small amount can cause the fork bushings to wear quickly and the forks will start to flex and become unstable.
Maybe the confusion is they're really only referring to the shock. I haven't spoken to either about it. You can extend the length and travel of the shock, but this will unfavorably upset the frame geometry. You could try and compromise by running a dual-stage rear spring so that any added travel is only realized as droop, but that's not going to benefit you as much as you might hope as it causes the shock to pump. The true solution out back would require a shock relocation and modding both the under seat tray and the subframe.
Another issue with the forks is the bottom triple-clamp. It rides approximately 25mm lower than a KTM thumper. You just don't have the room available for this kind of travel without building all new fork housings and stanchion tubes from scratch (~$10k). If I were to attempt this I would definately upgrade to a 52mm fork tube and increase the overlap. Unfortunately, this would raise the seat height by another couple of inches!
I believe shorty Adventure forks are 235mm, SER forks are listed at 250mm (resticted due to the aweful rear shock), and S forks are around 265mm. I run the max physically available without unbalancing the geometry... 277mm. Any more than that to me requires a frame redesign...
here's the page for Pyndon's setup. this is what I had been thinking about but as you said, the seat height of the SE is already pretty high, with more travel (unless it's sag) it's going to affect that I would assume.
also I would assume that he's making his own longer fork tubes for that price and like you said to keep the overlap but who knows...