Pipe Train Questions for Dummies

Warning! Model discussion ahead!
I have finally gotten around to finishing a string of pipe gons and idlers I started 7 years ago. They are San Juan, On3, and plastic, so I wanted to wait until I had some experience simulating the look of wood out of the things since there is so much unpainted exposed wood on these cars.
Anyway, I have some questions about the pipe trains I thought I could get some help from the group with.
1) In what year did the pipe trains begin to operate with such volume to warrant modification of High-Side gons into pipe gons?
2) What would be a good color(s) for pipe loads? I am using 10" soda straws for pipe loads, as they weigh nothing, and can be easily removed so the cars can be used or displayed either loaded or light, and no additional weight will be necessary.
3) In switching operations at either Farmington or Durango, it appears that eastbound, and in storage/staging at Durango, the idlers were commonly grouped together, as were empty pipe gons. Anyone know why?
4) Were at least some of the converted pipe gons from high sides used until the end of operations? I know a number of them survived.
5) what would be a common number of loads in a Westbound pipe train, and were these often mixed with regular freight? Were there trains of nothing but pipe?
Thanks in advance for filling in some of these questions. I know John Hammond knows plenty about this subject, and probaly several others do, too. In recalling the questions posed by Jessica a month or two back regarding the yard situation at Farmington, I recall there were several comments about how much trouble crews had switching the yard. With anywhere from 3 (min)to 5 (max) idlers necessary to handle only 4 loaded pipe gons, I find it very believable that the small yard would have filled up way too fast if the little pipe gons were used. The larger 40 foot cars would have made life much easier on the crews.