You think you have a good spin? I am guessing you might have an ok spin, maybe even a good spin but I'll bet you can't spin anywhere near as well as you might think.
I rode my SSRB in fixed mode on Monday and again last night and I now know that I have alot of work to do before I can say I have a good spin. The first ride was only about 7 miles and there wasn't many big hills in it. Last night's ride was around 20 though, and it had several big hills (1-2 minutes long) and was generally much more rolling. I have learned a few things in my two ride career riding a fixed gear:
You only forget that you can't coast once.
You only forget to not turn to sharp once.
Starting is harder than stopping.
Going downhill is harder than going up.
Standing to stretch is hard and must be planned.
Trackstands are much easier to do.
Bunnyhopping curbs, bridge joints or anything else is damn near impossible.
I have muscles in my legs I never knew were there ( I know now only because they @#%# hurt).
As you get tired, you tend to forget points 1,2, and 5. Justice is swift.
Any small inconsistency in your pedal stroke is magnified a dozen times over for every mile per hour you ride.
Going downhill at 27 mph will teach you to relax lest you look stupid and beat yourself silly with your kneecaps.
There is no resting.
There will be more to learn I am sure as I ride this thing more and more and I would think the awkwardness I feel now will go away. I rode for a little more than an hour last night and I felt like I rode twice that much after I was done. For training, especially winter training, I think this will be the ticket.
I can't imagine (at least right now) how people ride fixed off road.