Why not contact Kartboy? Because it's not a shifter-lever problem. It's a shifter (person) problem.
I have the Kartboy on my '01 and the only time I ever grind the gears is when I forget to push the clutch all the way in. I learned a long time ago that cars don't really care for shifting into 1st or reverse while moving. A constant pressure (not forcing) on the lever will get the synchros up to speed and it will slip in eventually. It takes a second or two. The RS has enough torque that you really shouldn't need 1st gear except when you are at a stop or doing a rolling-drag race.