If I used the prussic and fig 8 like in Angrysparrow's post with the original Hennessey spectra cord, would I ever be able to untie it?
The prusik won't be a problem, but the figure 8 is a serious pain to untie. That HH spectra is some seriously gripping stuff. But, it CAN be done - and I guess that's the chance you have to take if you want to try an alternate suspension. You'd have to add some sort of bight to your stock lines for most of the methods that are out there.
"Physics is the only true science. All else is stamp collecting." - J. J. Thompson