K.C. - I don't have a pigtail, but a few seasons ago I switched to a loop of Amsteel that's attached with a Prusik knot. The free end of the loop has an eye splice and a heavy knot as a toggle, to go through the clew.
That also results in a rather straight section of sheet (especially since mine does not bend easily in a tight radius). Hang-ups on the mast clutter are indeed rare.
The "shock absorber" effect is presumably because the clew needs to travel the whole length of your pigtail (double the length actually) before it's taught and can pull the sheet in the opposite direction. If the motion of the clew is less than 16" you get tugs only in one direction, making the motion of the sheets less violent - neat. Especially so, since Amsteel has no inherent shock absorbing qualities.
My loop is too short for that effect, but my sheets are so stiff/heavy that they dampen the system in their own way. (Not that I recommend such rope for sheets, I'm just too cheap to replace it -- and its' nice to know that I could lift the whole dinghy section of our fleet on that jib sheet