They age as a pair - spring rates change with age & use/mileage, and they are fitted new as a pair from the same manufactured batch - each batch will be different, albeit slightly. Ask youself the question "why does one spring break and not the other" (crashes aside)? I suggest one answer might...
I was led to believe that no ABS means an "even" brake balance - i.e. to much rear bias - hence the twitchy feel at the rear with non abs cars (e.g. 172 cup). While this is no way dangerous (like other non abs cars - learn to brake properly!) it can be a pita on the track and very difficult to...
Nick - go for it, still have a few (5) bikes in the garage but sold my KTM640 SM - just the best fun ever and so cheap on front tyres :-) Reckon they'd be a blast on a trackday too!
The Trophy is slick, direct and handles well but it won't show a new 911 anything on most roads (i have both so can comment first hand) - where the T shines is on pace versus cost, very little to compete for the money- plus its quite refined for a hot hatch and it's a ltd. edition. Maybe a 172...