Tom, when I drew the Simple Wiring Diagram I was using my 2001 VII Sport, it had a direct feed to the Start Relay, unfortunately a couple of years later the Guzzi factory switched the Start Relay feed to the ignition switch causing untold grief for owners. You can see the difference here. http://www.thisoldtractor.com/guzzi007/schematics/1999_V11_sport.gif 1999 era with a direct feed to the relay. My 2001 never had a problem with cranking but the regulator Voltage reference was the pits (through two sets of relay contacts).
http://www.thisoldtractor.com/guzzi007/schematics/2004_V11_Sport_Catalytic.gif 2004 with the start relay fed through the ignition switch, I would like to believe the factory are ignorant of the high current the starter solenoid draws but you have to wonder why they haven't spoken to the manufacturer about it some time in the last 50 years. Note this year has a direct connected Voltage regulator, that' should be a plus.
I assume you are having the dreaded click when you press the start button, that is caused by too much Voltage drop through the ignition switch, the starter solenoid is designed to pull at least 40 Amps while it is moving the gear into mesh, once engaged with the main contacts closed it drops to 10 Amps.
The Guzzi schematics never show the double coils in the solenoid, they are both about the same number of turn but one is of heavier gauge wire and draws 5 x the current, thats the one missing on the factory drawings. All Guzzi starters have this double coil even today.
You can probably improve things for a while by cleaning the ignition switch contacts but the real answer is to change the start relay feed from through the switch to direct but that involves changing the headlight relay wiring as well.
Another easy method is to add a new relay to the existing solenoid trigger circuit to boost the signal the trigger wire is removed from the solenoid and now only picks up the new relay coil, a fraction of an Amp, the new relay contact is fed from a new fuse direct from the battery, it can now provide as much current as the solenoid needs.
You will probably hear about the MPH solution, I don't think that will work with your bike, it would result in the headlight staying On.
I have never actually done one adding an extra relay but it has the advantage in that the original wiring remains the same.
The current of 40-50 amps will only last for about 20 milliseconds (as long as it takes to close the main contacts) then it will drop to 10 Amps while cranking. The current through the motor of course will be 150 - 200 Amps, no change there.
No need for a relay socket, just use spade lugs right on the relay pins.