I can do that! I did it before when measuring R on the paths in the 5er, using Salvo's method of putting the voltmeter across items when knowing the amps on that path.
I still have the lead with 30 ft of speaker wire and an alligator clip so I can check voltage drop from house battery all the way to the starter relay at the front.
With the 5er I ended up adding a long copper water pipe to the neg path in parallel with the frame path, and that made a big jump in amps converter to battery. Adding a long fat wire to the pos path made amps go even higher.
One lesson there was that once you get to max rated amps of the converter, there is no point in reducing R any further. In this case, there will be some sort of "current limit" from the alternator set-up at the front.
A point was made earlier here, that you don't want to run the alternator at high amps so much because it can't take the punishment--so it is not like a converter running for long periods at its current limit, which it can do no problem.
