Agree, I'm assuming a minimum of 2 1/4" negatives when applying pencil shading processes at the negative plane. Clearly it is easier with bigger negatives unless the manipulations involve only large broad areas. But the paper plane option is still there - applicable to any format because it only depends on print size, and offers some pretty decent flexibility for creative manipulation. All these selective masking techniques are more simple and more low-tech than silver masking, so they can be interesting options.