I have a photo that would illustrate perfectly, but it's on my computer at home and I'm at work (lunch break - not goofing off!)
It is true, having a gin pole at about 85 degrees is better than 90 degrees. There are a couple of reasons. First, the gin pole won't hit the ground when the tower is nearly all the way up, it will stay a foot or two up. Now you can take it off at your convenience, not during the raising process while 1000 other things are going on at the same time.
Second reason is a little esoteric, but I believe it's got someone in trouble before, so I'll try my best to explain it:
A gin pole is NOT a lever. A gin pole is a "column" under compression.
Anyone who thinks a gin pole is a lever may argue that when it fails, it bends. Yes it can bend, but that is due to compressive buckling, not a bending load. Or because the cables aren't attached properly. You need to have some respect for that compression load pressing down on the pivot joint. If the gin pole is attached in the wrong place, it can actually press DOWN on the base of the tower, preventing it from raising as you pull. I think this happened to "behoof" a while ago, but I wan't sure. It doesn't matter because he made many changes and then found an engineer to look it over in person.
If you want the gin pole attached to the tower, either you want the gin pole to NOT interfere with the tower's pivot at all, or they share the same pivot but must not flex relative to each other. Another way is to mount the gin pole on a pivot just in front of the tower's. I wish I had done something like that, as a matter of fact.
Another thing to think about is that once you start pulling on the cable, the wires stretch. The angle between the gin pole and the tower opens up a little. Not much, though. It usually doesn't matter, but in Behoof's case, I think it made his situation worse.
(Sorry Behoof, for making an example of you, but I think we can learn from your experience, so thank you for posting about your troubles)
It's coming a bit late, but here's some reading material you might appreciate:
http://www.sparweb.ca/4_Tower/Monopole.html
http://www.windenergy.com/documents/manuals/0028_REV_E_50FootWhisperTowerManual.pdf
SWWP seems to have re-vamped their website, so I'm off trolling for new information. Bye!