Bruce,
In this particular case the assembly is a first guess approximation for a prototype. At this stage the drawings are as much for my benifit as a designer as they are for future production. Using shown dimensions acts as a design check and since it's quite likely the dimension will have to be adjusted it's much easier to have the number on the drawing than to have to go back later and interogate the model. Open the drawing, enter the redlined values, save, print, done.
If the tool is too cumbersome to use in this manner then so be it. But if the capability is there and can be used with a little up front effort why not use it? In this particular case Show all produced just the dimensions I was looking for. That was largely because other dimensions on the drawing had already been placed. If there are other (better?) techniques for isolating assembly dimensions the knowledge will likely be of value in the future when the assembly is much more complicated.
Bernie Hayden
XKL LLC