Wow, you fellas give a hearty welcome of the most useful kind! Thanks for the excellent responses thus far.
All the fastening points of the racks will be directly to the supporting trusses. Morton pole buildings are a truss and perlon sustem. 45 feet divided into 9' bays with poles going down every 9'. There are large (2x trusses every 9' and then 2x4 cross pieces (perlons) that hold the metal roofing which runs peak to eve. There is no sheathing..
I am encouraged that there are no general "RULES" that say you cannot come closer than so and so close to the edges.
I would certainly have never thought of fastening to the rim or "flying rafter" of the building. That would be a definite recipe for disaster, at least based on common sense. When I re-roof a structure, I get nervous just working out there over an unsupported rafter (and not because I am afraid of hieghts).
I had not thought of the need for access to service the system. Am I going to have to dissassemble the array often? What's my chances? It will be VERY well grounded and pretty much zero debris. Is this a reason to buy one brand of panels over another?
The roof is 26.6 degree. Not quite latitude here (39) but steep enough to make walk around on it tricky. I was hopeing to not go up there for a good long while after I get it all done......
Well, again, thanks for the great advice so far.....