Ask that guy if he replaced the float with a new one; I am not sure what 'gone over' means exactly. A float leaking or getting 'gas-logged' is not always readily visible. I have had them look fine in a close visual inspection but yet still absorb gas and flood the carb. Looks like BBD floats are still available, with just a quick look online.
Trying the regulator may be easier... it just seems that 1/2 psi would not typically be a problem. Your gauge looks like a reasonably accurate one.
