Well in my opinion, the G25 would be compatible for 13/18 gears. When you reached 6th, you pressed a button to switch to the Hi range, and then 1st would become 7th/8th, 2nd would become 9th/10th, ect... (maybe I'm not numbering the gears right?) it wouldn't be hard, just a matter of making the same control for the 1st to become 7th when the button was pressed. Good luck on building the shifter by the way ;)

its extremely easy to use 1 switch for 3, if u get me. 1 switch could be easily made into 3 functions by the flick of another switch (range shift) check my other thread tomorrow i will upload the diagrams to explain :P

Yea no worries, I know what you mean. It's just a matter of making some sort of "trigger"

thats the easiest part, ive even found a way of implementing an 18 speed shifter and clutch into 18 wos :P my designs will be upon the forum within the next day

Ah yes! No more going trough the gearbox "up, up, up, up"
Thanks very much! I'm looking forward to look at your designs and putting them to work in my 18WoS :D