There might be only a few riders interested in this (or perhaps I should say crazy enough for this).  http://www.tourdashugel.com/
 
105 miles, 14,000+ feet of climbing.  Hills with 25%+ grades.  The best rest stops money can't buy (part of the ride organizers evil plan is to make you not want to continue).    The route has multiple returns to the starting point, making it easy to come to your senses and get off the bike.  The attrition rate is about 50%.
 
This is a free ride, donations are accepted for the Austin Yellow Bike project.
 
I've done this ride twice on my Merckx, when I was living in Austin and riding most of the hills, it is a bear of a ride.  Shellene did it last year (on her DF).  While I can't speak for the first two years, I know that no recumbent has even started this ride, let alone finished it in the last three.
 
Anyone feel like joining me as I try to "Do the demo" in Austin?

Don't worry about walking some of the hills, a lot of the DF riders do (including me in the past).  It really is a fun ride, if you are into pain.

How tight are the hairpins? We've had a private oval test track available once a year for a few years. It's 1.1 miles long near the infield with about 10' wide straights and I'm guessing about 200' wide infield. The surface is a bit rough which makes cornering at speed a little interesting when trying to dodge the dips, wheel-swallowing cracks and grass clumps everywhere but it's still pretty fun.