maybe my definition of long is different than yours

i would never have guessed there was an 8" shade out there. at any rate i have never tested it personally nor have i seen a scientific analysis so can only talk about theory. you have a LOT more experience than i do and i take you at your word. i think my shade is at least half the length of what you are talkinbg about so i am not going to worry too much.

i will say that the light collimating properties of a shade probably increase the sharpness of an image over the width of the lense. without a shade you get scattered light that comes from all directions and if your glass is not of the highest quality that will translate into soft image edges and flare in the image that may make it hard to find the sharp focus point. some lense shade length probably is a good idea but i really don't know what is optimum.it would vary from scope to scope. too long and it will probably narrow the field of view by cutting off the edges of the image. we see this in camera lenses all the time. if it does that it definately would act like a smaller aperature and increase depth of field making it less of an accurate rangefinder.