Now that you have your body marked for where you're going to drill the holes I use a *sharp* reamer to slowly ream out the holes.
Generally I will only do each hole a little bit at a time until they just start to slide over the body posts... this way if one hole is a little off you still have time to sort of work the reamer over in the direction you need to go without making the hole too gross looking or too big
I like to make it so that the body will just "fall" onto the posts and that once it's on if it's given a little lift up it will fall right back to where it was...
This way it ensures you that the body isn't tweaking the car at all and if you hit anything such as a corner dot, curb, etc, it will more than likely just upset the body of the car and not the car itself
I always try to leave some free space for the body to wiggle up and down a bit for this reason.
Now that the body is mounted if you left too much of the body left underneath the trim lines it will be a good time to trim them now.
The "sharpie trick" seems to work pretty well.. you run the sharpie allong the bottom edge of the body while the car's on a flat surface and this gives you a straight line to cut the body on.
Incidentally if you see that this sharpie line is WAY off of where the bottom body lines are I would encourage you to change your body post holes so that the molded lines are more or less the same as the sharpie line. This is two fold, if the sharpie and the body line are far off, your body height may be off and any excessive rake will cause the car to handle oddly.
If your body's rake was far off to begin with it might cause the body to "catch" on the body posts now. If this is the case I recommend just using an exacto knife to sort of "scratch" the body hole open slightly until it is free on the body post again.
This will ensure that you don't have too much forward or backwards rake in the body too..while it's a valuble tuning tool having too much one way or the other will definately handicap you.
Ok, now your body is mounted flat and square on the car, it's free on the body posts...it's time to cut out the wheel wells!
I usually take an old tire and line it up with the axles on the car... you might want to put your template tire on "backwards" so that the hex is facing out so that you can more easily line up the axle with the hole in the rim.
I then take a sharpie and trace along the outside edge of the tire.
Next, I get some good curved scissors, and cut allong the outside of this line as a starting point.
After the initial cut, press the sides of the body in to see where the body will catch on the tires and remove little bits as necessary, all the while trying to retain the "roundness" of the wheel well at it's top half... at the bottom half I generally cut it down more straight because when the car is actually running the tires generally have a way of going down at full droop and this can catch your body as well as at ride height.
Also be sure to turn your front tires from side to side and see if it will catch badly as well.
I usually try to radius the edges where the wheel well meets the bottom edges of the body to just smooth things out and lower the chances of a sharp edge catching on my tire.
To be continued!