As another note, you don't have to use Triumph branded shims; they're four times the price and my dealer doesn't keep them in stock, not to mention the dealer is 80kms away. I go to my local Yamaha dealer and get the shims there. The shims are pretty generic, 24 or 25mm diameter I think.
I personally would never use a caliper to measure my shims, it's not precise enough, especially when you can go to a local machine tool supplier and buy a cheap micrometer for $15 - 20.
I think cams are a good upgrade too, but all the Triumph ones are crazy expensive compared to other brands of bikes.