another amp meter bypass question?

I'll be doing this in the next few days and plan to pass new wires through the bulkhead fitting without any connections.
One thing I plan to do differently than suggested here, tough, is connect the voltmeter to ground on one end and the other terminal to a light ga wire soldered into the under dash splice MAD shows. This way, the guage will read the voltage drop created by the ignition, headlights, etc.. Essentially everything that uses juice except the starter which shouldn't be connected to the volt meter anyway.
Then, if the voltmeter shows discharge, it will say that the alternator isn't keeping up to what the system requires and the problem needs to be addressed.