Hi, I am a big guy who has put (around here it isn't much) 20K on a stock seat. This includes 6500 miles on a trip last summer. I did a 800+ mile day, and have done many 400-600 mile days but it is very individual, as others have said. I've tried beads but not much else.
A custom seat is in my future. In the meantime I have been talking with my brother who owns a 'Wing in Boston. He gave me a cheap solution I am going to try. I was going to try it then post the results on the forum later. It is a rubber, celled pad encased in a cover, about the size of a GoldWing seat. LD riders there say it helps (more than beads I hope). The details are in the following thread in a Wing forum:
https://gl1800riders.com/forums/showthread....rt+seat+cushion
The UPC code is: UPC number 23034 08640 6
Cost: $20 at my local Wallyworld
Warnings (per the thread): Do not leave in the sun as it will burn your backside; do not rip the label off because the cover rips.
Various permutations are discussed in the thread, including doubling up two in one cover, throwing sheepskin over a cushion, etc.
I bought two and my wife stole one for her hard computer chair and I haven't seen it since. I put one on my chair and now I'm buying two more for my project.
I'm going to put two of the celled rubber inner pads face-to-face, cut to the size of the stock FJR seat, then have them sewn into one cut down cushion cover. One problem it does cause is seat hight. You mentioned a shorter stature, and this solution raises seat hight about one inch. But for $20-$40 (whether you use one or two pads) it is worth a shot. Also not a bad idea if another solution you choose isn't working -- you could try the Walmart pad on the road.
Good luck on your FJR ownership journey.