21" 1985 Trek 620 Cirrus with 700x41 Surly Knards. I have Schwalbe Marathon Supremes in 700X35 which are my favorite tire, and I just ordered some 27 1 1/4 Marathons to try as well. I have them in 26X50mm in on another bike and they have been bulletproof with good rolling capabilities and while not supple still very predictable. I'm getting the cockpit and fit figured out then I'm going to get into the brakes and drivetrain.
So far its a fun bike to ride, I haven't noticed the flex I have on my road bike under torque but I guess I'll have to pay attention to compare. My Lemond road bike seems to call my attention to its flexing.