asym rigging

[mrgnstrn]

I am interested in the asym setup that has two sheets run to a pigtail that is attached to the clew of the sail.
(see www.layline.com for a picture, if needed)

Since my boat is not really designed for an asym (it is a 1987 C&C 35 MK III, pre-asym days), what is the best length for the pigtail?

I see that J105s use 18"-36". Any experience out there say they should be longer? shorter? toward the long end? toward the short end?

Also, if you use spectra or some other 12-braid for the pigtail, does it take easily to knots like a bowline to attach it to the clew of the sail? or should I just put a small snap shackle on the end of the pigtail? or a spool shackle?

Thanks,
Keith