I sympathise with you dude... I have just had to do the same. I have put 1300 miles on my America in 2 months and although it has been fun, I've been plagued by 'tailbone' ache on every ride. It was getting to the point that I would not look forward to my next ride on the bike.
The first 30-40 miles would be fine, but then the ache would start to kick in and no amount of shifting around on the seat (gel seat too) had been able to help. After 50-60 miles the pain would get un-bearable and I would have to pull over and walk around. This was not good, as in 3 weeks time I'm off on a little jaunt around northern france putting in around 1500 mile in a week.
After reading up about it on the net I have now opted for a different style of bike which takes the pressure of the tailbone.
As I originally started riding to do some touring, I looked a the Triumph Tiger and Sprint ST and I have just had a 2010 Sprint ST on demo for two days. Totally different to the America I know, but it has just allowed me to do 200 miles in comfort with no tailbone aches to report. Yep, it puts a little pressure on your wrists and I was at first wondering if this would be its achilles heal, but that has not been an issue on the demo ride.
To be honest, I was quite blown away by the ride, it felt so sure footed and confident. The way it gets up to speed ;-) and cruises at motorway speeds gives it great touring potential. Also, after riding 90 miles on the motorway, I peeled off to do the long route home on the twisty roads and it was bloody fantastic fun.
I would have looked at the new Sprint GT, but its not out in the UK until August.
So, I'm sadly saying bye to the America - a fantastic bike but just not right for me - and I'm picking up my new ST next weekend!
