Using 2 alternators .....

Can you say overkill!

If you check your voltages when you are at maximum draw and it is greater than 12.6v you don't need more generation capability.

If you really want higher voltage under a particular condition get a variable voltage regulator and crank it up to 11


Devices only draw the current they need, not the max they are rated at. (Heater coils and incandescent light bulbs are the exception)

If you just have to do the dual alternator, I don't think you will need any special electronics. If one alt and voltage regulator is putting out a bit more voltage than the other they combo will find its own level.

Two batteries in parallel gets 2x the capasity and will both be at the same potential.

Think 2 locomotives each one adds power to the system.

If you want a few more hp. Disconnect the field wire to the alternator. No charging from the alternator but also no load on the engine