How do I calibrate new tesoro coil on B3

[grayfray]

Hello, can anyone tell me how to calibrate a 8.5 inch widescan onto a Laser / Tesoro B3?
If it helps I have found the small trimmer switch on the circuit board and I know i need to use a peice of ferrite.

[grayfray]

pics

pics of circuit board and trimmer just out of view of first pic.