Hi PMI.... Vickers (Maxim license... then improved) was much earlier than mechanized stuff. But for the heck of it, I did some research to see if, later, they put in a different feed block or created a 'switch' side. Could not find anything, so I think they were limited to a right belt.
Biggest problem I am having with mine is the now... very... antique canvas/cloth belts are just jamming.... I have a couple of ideas... including trying ironing them. But one of these days, someone is going to need to put these back into production! I also want to try some of my Russian Maxim belts. They look like they would work.... Next time I need some Vickers therapy!
Cheers,
Sirhr