Ok, so Epic may be a bit overly dramatic. Anyway...
I decided that since it wasn't such a horrible experience the first time, I'd give this whole fixed-gear dirt riding thing another go. This time, however, I decided to step it up a bit, opting to ride my go-to loop in Reston.
Since this loop is significantly more interesting/challenging/rocky/rooty/hilly than my first fixed outing (@Wakefield), my plan was to only ride a portion of the ~10 mile loop. I figured I'd head out 'till I was half-tired, then head back to the trail-head.
Much like the first fixed dirt ride, I found that riding these slightly more interesting trails wasn't nearly as bad as I expected it to be (even with the 32x15x29er gearing still attached to the bike). I pretty quickly reached my first planned end-point (the cricket fields), but decided I felt no worse than a normal ride, so I pushed on, planning to make the halfway point of the loop. Once there, and still feeling good, I figured I could turn around and head out the way I came, or I could simply finish the loop. Since the second half of the loop has far less climbing than the first, the choice was easy. I continued on and made it to the end of the dirt portion of the ride (~8 miles) in decent time and feeling pretty good (aside from that pinch flat that I had to repair along gang graffiti row under the highway overpass - yay). All that remained was the ~2 mile paved bike-path ride back to the car. At this point, my lower back started bugging me quite a bit. I'm guessing that it was a result of either having to pedal every inch of the preceding 8 miles, or of having to strain like a bastard to make a few (aka "most") of the climbs. Whichever, the last mile was not terribly enjoyable.
On the whole, however, it was a great ride. I made all but two of the climbs (which is about par for me, even with a properly geared ride). I'm hoping that getting a correct size Tomicog will lead to easier climbing and hopefully less back anguish on future rides. I'm still leaning towards running fixed at a certain beercentric ride in the not-too-distant future. Gotta put in a few more rides with the right equipment (cogs, not beers...tho, now that I think about it, beers might help too) to be sure I'll survive the experience.