With long cranks and long cams you get too much flexing and twisting. On some 12 and 16 cylinder V or boxer engines in the past, the power has had to be taken off the middle of the crank to get around this.
On modern Top Fuel drag cars, the cranks and cams are designed with a twist already in them, so that when they hit the throttle, the flex due to power actually makes them straight.
No reason I can think of to go longer on an engine than a V10, or even a V8, really. Boost solves a lot of problems.
Nick