Absolutely no issue with VOSA. So nothing to worry about there.
If I were you, I’d establish the capacity of the tank (sometimes embossed on it), fill it up and allow no more than 10 mpg. Don’t run it anywhere the limit. End of problem.
For a long time we ran a service type bus that had no gauge and this was the method used. Similarly, many years ago on 1960’s trucks. Either no gauge or not working.
Hope this helps, Pete 