Got my hands on an older XTR rear derailer. Was thinking of replacing a lower grade derailer on a recumbent. The existing derailer on the recumbent is "standard". This XTR works in reverse - the spring pulls the derailer onto the larger cogs and finger force pulls the derailer onto the smaller ones. I had never seen a derailer that works this way. What's up with that? Was this a design that was tried for a bit & abandoned? Can I / should I swap these derailers? Will it work?