Old Fella,
If I recall, the 707's 35-degree sweep-angle figure was based at the 1/4-chord mark (I think it was around 37.5 at the leading-edge); the 727's 31.5 degree sweep-angle was based at the leading-edge as far as I know, with the sweep at the quarter-chord being 28.5.
trimotor,
Jane Doh: the 727 wasn't poor in terms of directional stability - just that the latreral stability was very strong. (courtesy, probably, of the amount of wing sweep).
Okay, I understand