One of the problems with the lateral chain and sprocket drive of the conventional bicycle is that the right side (with normal right side drive train) of the rear triangle undergoes compression from pedaling forces. This tends to pull the rear wheel to the right. This force (and the corresponding reaction of the wheel) varies proportionately with the ratio of the chain line distance to the chainstay length.
In other words shorter chainstays equal tendency for the rear wheel to skip or hop sideways during high pedal torque and even more so when using the higher (more outboard) gears.
Dan Christopherson
Lopez Island WA