Perhaps my rump is as hard as my head, but I've been riding a plastic Unica since perhaps 1975, same saddle, and I don't mind it. If I've been off the bike for a while, I'm a bit tender after the first ride, but then there is no trouble.
And, unlike the original Ideale saddle, there's no leather dye to keep rubbing off.
Even the ventilation holes in the saddle (since the plastic can't breathe like leather would) have not been a source of chafing, as some predicted.
- Joel Niemi / Snohomish, Washington, USA