I couldn't stand the suspense any longer, so I went and set up a test with a reducing resistor. I used a 1.35 ohm resistance in series with a 12V supply to a 6V AD radio. I monitored the radio voltage from cold to fully warmed up and it worked perfectly. At cold startup the voltage dips to about 5 V for about 5 sec and then it levels out at about 6.5 V. I can see no problem at all with this approach.
I have read so many negative comments about using a resistor and I really see no reason to fear this method. I would suggest a resistor of about 1.2 ohms and at least a 40 watt rating.
