I realize your primarily interested in comments about the passenger seat, sorry, I can't offer anything about it since I never ryde two up.
However, I must say the driver's seat on my 2016 F3-Limited SS is the most UNcomfortable motorcycke seat I've every sat on. I cannot ryde more than an hour without serious discomfort. There seems to be three "hot spots" that are particularly bothersome; the ischium area, both sides, and the prostate area. The Ischium forms the lower and back part of the hip bone. When sittin, the body weight falls on the Ischium. I've only put a little over 2k miles on my F3-L since Jan 26th, it's just not fun to ryde when your butt hurts. I averaged over 15k per year on my previously owned Spyder RTs.
I have a Russell Day Long seat on order. Unfortunately for me they are really busy this time of year so my seat won't go into production until 31 May and not received until mid to late June. Looking forward to ryding in comfort the second half of this year.