kairles: if you need some detailed suggestions on cutting your plastics, I'll walk you through the method that I used for my frame sliders. I came out with a perfect 1/16th of an inch all the way around mine with the method I used.
Tools needed
-hole saw thats same size as slider that goes through plastic
-small diameter pilot bit
-drill
-pliers
-modified motor mount bolt (see explanation below)
-rubber mallet
-dremel with sanding disk
-extra long drill bit that will fit into pilot hole portion of hole saw
1) get a bolt of the same pitch as the motor mount bolts (im assuming that the rail mounts to this bolt as the frame sliders do) but longer.
2) cut the head off said bolt and sharpen end to a point thats centered on bolt. I did this by using a bench grinder while rotating the bolt.
3) remove fairings and take out the motor mount bolt on one side where slider/rail attaches.
4) put modified bolt in and thread into the hole using a pair of pliers to grip the bolt, and make sure sharpened end is facing out.
5) when bolt is threaded in, leave enough out so that the point will hit the plastic when reinstalled.
6) mock up fairing back on bike, and secure with a couple of the bolts.
7) GENTLY tap on plastic all around the area where the bolt is to put a mark on the inside of the fairing. if it goes all the way through it this is okay, as you're going to drill through it anyway.
8) use pilot bit to drill through plastic (you how have a hole thats dead center on your motor mount bolt)
9) put extra long drill bit into hole saw.
10) put fairing back in bike and secure in place with all bolts.
11) (and this is the hard part) slowly move hole saw pilot bit into pilot hole. Make sure that the pilot bit is sliding into the hole that the motor mount bolt slides into. (This will insure that your hole will accomodate the slider's diameter. hole will not be perfectly round, which is what you need) and let hole saw contact plastic until it's marked approximately half way around the diameter of hole.
12) remove plastics and line hole saw back up with marks made when plastic was on the bike, and drill the rest of the way through.
***note - as said before, hole may not appear perfectly round, but this is to be expected. plastics curve on the bike here, and hole has to be somewhat ovel to present round face at perpendicular to bolt/mount for slider/rail***
13) when all the way through, put plastic back on bike and test fit slider/rail
14) if hole is too small, use the dremel tool with sander bit to gradually enlarge hole until it fits.
15) repeat for other side.
At this point, you should be able to reinstall your plastics and then install your sliders/rails with a good fit. I went back over the areas I used the dremel on with a small rat tail file to get rid of all burring.
One other thing that I made sure of was that I never had more than one motor mount bolt out at a time, because I was concerned about things shifting around and not lining up when putting back together.
yes, I know this is long and detailed, but it worked GREAT for me. Just take your time and go easy on it. PM me if you have any questions.