I recently added a Brooks Flyer Special to my Strida 5.0 LT. Love it! More comfortable than stock and the springs seem to really soak up many of the bumps. Along with it I added the bended bars which for me, whose 6’2" tall, was a big improvement in fit and general feeling of stability.
I choose the aged leather seat to avoid having to oil the seat and because my seat will rarely see long term sun exposure or inclement weather (here in California).
I had a bit of a struggle getting the seats mounting rails to snap onto the plastic Strida seat bracket. I had to push and wiggle for 20 minutes before it finally slipped on. Once in place the seat frame fit well without any clearance issues.