The sin(5degrees) is .08715574. Multiply this by the width of the board to get the DIFFERENCE in the lengths of the two spacers. Assume center of spacers for simplicity.
The sin(6degrees) is .10452846. Ditto
You can see that the best you will be able to do is an approximation of 5-6 degrees.
After completing the jig/sled, part of the setup is to adjust table to correct for the angle deviation from desired 4 degrees. It was intentional to over shoot 4 degrees so as to be able to adjust table AWAY from its normal 90 degree stop.
I find it interesting to note that Nick's sled was 5.9degrees. The sin(5.9degrees) is very nearly 0.1. A much easier figure to work with than the multi-digit numbers above!
SOOO dooo what they did...make spacer length difference 1/10 spacer separation.
GOOD LUCK!!!!:)