Gipiemme did a cyclocross saddle in the mid 90's which I used for a while - it has a 'leaf spring' at the rear which absorbs the bumps - I wouldn't like to say whether it would suffice as a solution - I would say it's a decent saddle - alas it's difficult to match to many frames in terms of it's looks and is somewhat garish for a classic ride. Still available here: http://www.byckasport.co.uk/sport/index ... 1&Itemid=1
I'd question a suspension post for off-road just in terms of the riding dynamic as you have suggested but I think all you can do is try both a new saddle or seatpost or a combination of both.
Rick Powell 753 Track / Ribble Gran Fondo / Colnago Asso / 1975 Harry Quinn TT / 1990 Concorde Prelude / Vitus 992 / Keith Coppell Lo-Pro / 1986 KAS Vitus 979 / 1995 Mercian Strada Speciale / 2011 Raleigh GAC Militis 3 ex Graham Briggs / 1995 Ribble 7005 / 1986 Alan Super Record / 1985 MK1 Vitus 979 /
On the bench: Sirius 853 TT / Sun Solo Chrome / Ciocc Designer 84 / Giant TCR0 Pro Compact / Ribble 653 Tourer / Daccordi Lo-Pro / Look KG96 / Bottecchia Equipe / Look KG231 Credit Agricole / Contini Grand Prix / Aende Lo-Pro / TVT / Langdale 653 Pursuit /