Look at the FW190 build by scigs30 to see a picture of a nose block. Although I don't think his is adjustable. The ones I have seen have a very small screw at the front of the thrust button. Turning the screw one way or the other causes the thrust button to deflect a small amount. It's a trial and error kind of thing. Crank in a little bit of down thrust by turning the screw, wind up the motor and launch. Then make small adjustments with the screw until you get the flight behavior you want. It would take a whole page of writing to explain the process, someone could show you in 2 minutes.
Here is a link to a photo of fixed downthrust shim. The principle is the same
but, to make adjustments you have to glue in different thickness wood.
http://www.virtualaerodrome.com/image_d ... 42&offset=
If the link doesn't work look in my hangar at
www.virtualaerodrome.com
of my Fairchild 24.