Its all about the strength of your wrist I have met only a very few individuals capable of fishing any thing over 10' for more than an hour or less. However the few that can really throw alot of line a long bloody way.
The best of the 11' graphite rods is the loomis euro. But be warned the tips on these extra long single handed rods are very fragile and will break even if you do everything right. So guarentee is crucial on these rods.
My honest recomendation is to take a good look at the catalogs and stay under 10' in an 8wt. Have a good time sorting it all out!