Increasing your machine pre-roll may actually reduce your lockup times. The reason is that when PT is master and you do online play with machine control and a USD, PT performs the following actions: 1) Locates DAE and Primes it for playback. 2) Locates the Serial Machine. 3) Plays the Serial Machine. 4) When the USD locks to the timecode PT does the lockup magic to trigger playback. The problem comes if the USD doesn't lock to the timecode in time for the location that DAE is primed for playback. This forces PT to relocate and Prime DAE. If you increase the Pre-Roll a little you can avoid this situation and get more consistent shorter lockup times.