I took a closer look at my Checkpoint over lunch hour . . . it appears the point of interference might be the front derailleur. Especially if you've got a big front derailleur or one that hangs back from its mounting bolt, it's closer to a big rear tire than anything else. The seat post has a cut-away to clear the tire, but the front derailleur hangs back farther than a non-cutaway seat post would have. But again, if you adjust the rear axle to provide a longer wheelbase, I can't believe it would be a problem.