VW, There is a small window cut in the underside of the chassis to allow you to tighten the pinion set screw once it is on and in place. I run 93/47 64p with a RevTech 17.5 in GT2 in my Worlds. When I change the pinion I just need to pull the belt down a bit to allow me to get the pinion out. Accessing the motor screws is a different story. That takes a bit of time and dis-assembly to accomplish.
Nick, That is good to hear. As for the screws for the spur holder I don't swap spurs often enough to worry about it. I do as much research as possible to see what gears will be needed and gearing range will be needed to run with the motor/class I am looking to run in. Saves time and frustration.
Jason