I used the same relay setup on my 360. The system works really well and minimizes excess connections between battery and coils (only a fuse, relay plug and relay contacts). So, your getting the cleanest, most consistent power to coil. Another bonus, if your relay ever fails. You can pick up a replacement at any auto parts store for $5.
I will probably incorporate the relay system once I convert the 100 to 12 volt. Getting parts collected (350 stator) now. My sparckmoto R/R is in the mail, just need to pick up the 2.2ohm resistor to add to the coil. Bonus all the leds Ive already installed can use 12vdc. 8)
W the 125 no need for this. But, I also installed a Heavy duty, 20amp, dpst, spring loaded toggle from Mcmaster as my starter switch. That way it kills the power to the lighting system, free-ing up all battery power to the starter selonoid/ starter when I press it, then it snaps back to power up the lights, once the bike is running.