So I have been reading as much info as I can find on how to improve on the power/torque to the wheels. ( I'm a sled guy and know lots about CVT's) I have bought the shims, is the purple spring in the secondary still the thing to do?
Bike is 2015 grizzly 700.
C.V.T. mods. change the way engine power is applied to the transmission, and the transmission on a grizz is like a drive/overdrive gear box on a truck.
The stock grizz comes with a tame pulley ratio suitable for the the average rider and the ratio can be changer.
You asked several question in your original post, about shim and slugs and spring, so here is my take on your questions.
I don't think slugs are beneficial for most riders. Changing the engagement r.p.m. of the wet clutch shoes is not as important as changing the pulley ratio so that when the wet clutch engages the engine has the ability to turn the pulley with the available engine torque produced.
I learned to raise the pulley ratio with the stock wet clutch and 26.5" true tires and to do this I started with shims. My 660 will hold 2.5 mm's of shim but most 700's only accept 1.7 mm's max without cage modification. I found with 2.5 mm's there wasn't enough improvement so I had COOP machine the movable sheave which produced the benefit equal to around 3 mm's of shim on low end, and with the new taper angle to the belt face there was no change of top ground speed when the belt reached the out edge of the primary pulley.
I run a stock belt, and with the 2.5 mm's or the machined primary individually I experienced no belt rub.
Once I learned what the machining did for my low end performance I started adding shim with the machining for even better low end pull. Once I got over a 3 to 1 ratio the belt started to rub slightly, but I learned a little rub was not bad as long as the belt didn't rub clear through the cover.
I should add I added a purple spring early on and found it was the best for my application. I recommend using the lightest spring tension that keeps the belt from slipping.
From 3.1 to 1, I starting rubbing the belt in by slightly raising the ratio, I was able to get to 3.54 to 1, but remember I run a 660 which is know to have more room to play with (cover thickness). I have install enough mods. to get to a 3.75 ratio with the cover off but did not try to run that ratio on the trail. I learned with stock 660 axles anything over the 3.54 broke axles, so I stopped there.
Most members have stopped 700 C.V.T. mods around 3.1 to 1 and use a purple spring. That is the point they don't want to chance rubbing a hole in the cover.
Once you get there, engine mods can help.