Have confirmation that the pylons are 6 metres apart for the Siso GP, but as it's a practice obstacle the object is to gradually reduce the distance between them down to 4 metres.
On the matter of practice obstacles, our friends in Japan have let us know about the Trykhana or TekeTeke obstacle which really tests your ability to transition from full power to full brakes and back again.
Here is a diagram from a Japanese website http://caramel.xsrv.jp/hgc/trycahna.html
Here is a video of a rider having a go at it.
Dedicated to the wonderful sport of Moto Gymkhana