I have the EFI Classic 2014/15 with the solo and stock pillion seat. My wife finds the pillion uncomfortable as not wide enough. It is not wide enough, it wants another pilot's wide solo seat back there for her, shortened nose maybe.
I have removed and replaced the solo seat springs with very solid steel brackets, front fitted by usual 'dual seat' tongue, centre (rubber bush) bracket modified to clear the seat. The ride is much more comfortable for me. Rear shocks on second from softest setting. Rides are anything from 5 miles to 50+miles on rough lanes, no problems. The solo seat springs pogo, constant bouncing and wallowing is uncomfortable, very little feel of the road, disconnected.
Two-up with rear shocks up to 4 or 5 doesn't bottom out with my own 15-stone and wife about the same aboard. Wouldn't like to do a long run but 20+miles is ok.