avoiding getting saddle sore and tired ?

[5hark74]

I just finsihed a short trip on a 1150GS doing bout 2000km in 3 days, and am looking at going up from South Africa to Tanzania in a few weeks on a R80GS, and been wondering how I can reduce the strain I put on my rear. After the three day trip, I have to honestly say I was seriously saddle sore. I am looking at putting a sheepskin cover over the old GS to limit the strain, but is there some general advise out there that one can do to train the rear to not complain so much.