Dear Chuck;
Your right; It's dangerous and you must be carefull.
The one we tried the 6/8 usage on was a a 54 Ford with a (12V) 57 Lincoln engine, in 1960. When we got it to charge the Batt. lamps would blow (not right away). When we set it lower the battery wouldn't crank the engine.
As I recall a 6V system's range is 6.8-7.7 volts which will not maintain a Marine/Tractor battery etc.
Your friend may have used a tractor generator or didn't drive it much.
WOW how time flies. There haven't been 6V autos for 50 years. :p I just bought two 6V batteries too. One for my 52 Chev coupe & one for my 37 Chev P/U which both start right up.
