For me it was carpel tunnel and some nasty shoulder stuff. I have great core strength, and riding position was not the problem. I found my solutions, and posted it above. I also love my airhawk. I'm super skinny and even bought a gel seat from here and donated my pretty much brand new stock one to the forum as a roving loaner. And yes, I have no problem hanging off like the rest.
Mileage is something that is legit. You do build moto muscles. Hard to explain, but it's true. I live in a place with a very short riding season. I still put almost 20k on it last year. Probably one of the shortest in the lower 48.
My first ride this year, not joking, first, was 800 miles in one day. Was I a bit more tired than last year when I pushed her through the snow to rest for months, yes, but I could feel the nerves in my fingers and did it just fine. Like a first date with a soulmate.
Try some stuff, see what works. Start with the cheap fixes. And yes, I bought a carbtune from the owner in England, and it made a world of difference. I add them up to allow me to sit on my bike and point it anywhere for as many fuel ups as I feel is fun, and I'm not screaming. That would be like a very bad marriage where you think and you feel so much love, but just get pain, or worse, numbness, as a thank you.
/FZ6 bike counseling session. Leave a tip to the forum hosts.