"The descriptions of the hexamid leave me with the impression you have a fixed guyline distance, and for optimal pitch you adhere to those lengths (since length would determine angle)."
Fixed lengths are guidelines for an optimal set, yes. But there is no reason not to have longer lines, except weight.
On my (cuben, no stretch) Plus I have long lines, each with a fixed loop at the end, and I added LineLocks at the pull-outs (horrors, More weight?!) to make things easier for me. I did this for All of the lines, just so I could move a stake to avoid a rock or other obstacle.
It seems like every pitch has at least one line that requires several attempts before I get a stake in. I swing a small arc, and if that doesn't do it I move out and try again, and again, till I get it.
It's fast and when I'm done with a pitch the Plus is Tight. I only have about 40 nights on it along the JMT, the Winds, and in Colorado, so there are still opportunities for a poor pitch. But I'm guessing it won't be due to line and staking issues.