Rob, first you have to find the Voltage Regulator relay (the other relay is the Charge Relay that drives the charge light on the dash).
Under the regulator is a big resistor - this will go between the Common and Normally Closed contacts of the Voltage Regulator relay.
On this relay you want to bend the armature away from the Normally Closed contact. That is, you want to make it easier for any voltage applied to the coil to move the armature from the Normally Closed to the Normally Open contact (this action reduces current to the field coil of the alternator).
I don't have the regulator in front of me so I can't say exactly where to start bending but if the above makes sense it will give you a starting point.
Be interested to hear how you get on. Mine has settled down to under 15volts after my "adjustment" a couple of months back so it is worth trying.
Pete

