I think I forgot to check the box on my original post to tell me when replies were posted (or else they all went to my spam folder?), so i sort of forgot about this thread! anyway, thanks for the suggestions. and yeah, i kinda decided 90 minutes (each way) is too long for a sub-par saddle. now my plan is, if i do ride the bike the entire way in, i'm just going to ride the bike that has the brooks on it and lock the entire thing up somewhere as secure as possible (either inside a building or inside a bike locker). i know about locking the saddle up separately, but yeah, find the thin cables not very reassuring. i think i would only feel comfortable relying on a thin cable lock for the saddle if locking the bike up for a short period of time.

unless i somehow manage to have a change of heart re: foam saddles, i think i will also continue to go with my plan of only using one of those for trips of ~20 min. or less on the around-town bike.