I'm reasonably confident that Eric has done the mods. But to be honest, I never liked the performance of the little RS SPL meters. I see them as a way to get ballpark figures, but nothing more.

As for electro-mechanical specs, they're not quite as hard to get as response measurements because they don't include the acoustic domain. If you have a good signal generator and a scope or meter, you can obtain reasonably good T/S specs. I don't expect home measurements to be as reliable as those obtained at large shops with better systems. But still, you're really just measuring electrical values, and the mechanical transformation is reflected in them, showing electro-mechanical specs. There isn't as much outside influence as there is when making acoustic measurements, so you can usually expect decent results.

I think the best thing you can do to reduce ambiguity is to verify with more than one measuring instrument, and to ensure you can reliably repeat your measurement values.

Wayne