This was posted here by Roy Brown last November. It is for a Negative Earth bike with a solid state Rectifier/Regulator that has been converted to 12 volts (two of the Alternator outputs are ganged together).
Is this how you have wired your Arrow (ignoring the conversions if appropriate) ??
The output side of the Rectifier goes straight to the battery and the design of the Rectifier shouldn't allow a back-current (apart from a minute drain) under normal conditions.
From memory, the Earth connection is actually via the mounting bolt.
I can't see where you would get a massive drain from the battery if the Rectifier is wired correctly. If it was faulty I suspect you could get a current drain. The fact that the Rectifier was getting hot suggests that you might have the battery wired to one of the Alternator input connections and the earth wired to the Rectifier output. Does the wire colouring match the diagram ??
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH