Stop making this more complicated than it should be. Negative film gets extra exposure to saturate(expose for shadows), reversal films get underexposed(expose for hi-lites) to saturate. Metering a gray card when possible, especially including a shot of the card will allow the printer(lab or home) a benchmark to go from. Using the gray card to meter will give accurate exposure. Variables such as wonky meters and or shutters be damned, you should already know what your gear is doing, and if it's whacked, fix it, dump it, or know what to allow for difference.