Drew, I'd appreciate it if you would stop with passive aggressive assertions and assumptions, and tarring whole groups with the same brush. You consistently have something negative to say about someone.
An 81C is a 1/3rd of a stop difference. I don't know what situation you're advocating it's use. But in my situation, crossover becomes moot, as reciprocity failure wont be identical across all layers. It doesn't stop you from getting a neutral grey scale (Though a neutrally balanced grey scale may not necessarily be desirable) via balance. Delta E will change, but it's going to no matter what you do in the situation, you're not going to get the same Delta E you're used to in regular scenarios.
The most needed thing in my situation if I wanted a more 'normal' image is more exposure, not filtration. More exposure would do far more good then filtration, the amount of improvement would be a -lot- more then what filtration brings to the table, the improvement with filtration would be very minor in comparison, but still requires more exposure anyway, which could not be given at the time, so would only cause more damage, and a thinner image in my situation.
I sometimes use an 85 series filter in forests, once compensated for with exposure vs without filter (At normal non-compensated exposure), the same balance (as in neutral grey scale in each) gives more saturation for me.