[Roadsters] Front Calipers

[Mike Harris]

Re: Caliper location, the calipers piston housing has different size (in depth) threaded areas for the brake lines. The inside piston will have the bleed screw up (or a deep threaded hole for the bleed screw and ball) the outside piston deep hole will face down. Your lines will tell you the correct location if you get lost, (deep holes for bubble flare or bleeder screw other holes take inverted flare)  it doesn't matter the piston location as long as you have them turned right to accept the lines.
Also I think the needle is is to keep the piston from returning all the way as the brake pads wear, someone else may know this for sure. 
Hope this helps