Side note: If you don't shorten the dip tube, the only consequences are that you'll get trub etc in the 1st couple pints, right? Should it clear up or would you continue to get "dirty beer".
(hey, that sounds like a band name...)
That is true if you are serving a keg in the "standard" vertical orientation with a hand pump, but if you are serving a gravity cask on its side the dip tube will be in the middle of the keg (meaning you can only serve half the beer). Alternatively you can also get an extra gas dip tube and use that on the liquid side.