SternPerch Seats
I installed SternPerch seats on my 88 Catalina 30 in/around 1995. They fit well and were resonably priced.I believe your 1987's sternrail is the same as mine. Please see the link below. They have a single leg which rests on the aft lazerette locker lid, which can get in the way sometimes, but since they can lock in the 'up' position, I just tip them up, lock them, then open-up the lid (while avoiding the Sternperch's leg). The leg is also removable on mine with just a wing-bolt, so for extensive work aft of the wheel, I occasionally remove the legs and just leave them tipped-up.Hope this helps.