I have been thinking of updating my Extang Black Max snap cover with either a Lomax or a Truxedo Sentry CT. The Extang has been serving me well and realized this Sunday that the additional height provided by the bows of the Black Max (particularly the center of the bed) has bailed me out on at least 4 occasions. If I had a low profile cover I would not have been able to drive with the cover closed. The height in the bed with a cover seems to have been overlooked in the discussions of tonneau covers.
On another note today is the last day to purchase a Truxedo Sentry 15 and get a $100 rebate credit card. I'm running out of time to save a $100. In addition to reduced height I believe the rails of the Sentry stick into the bed 3" on each side while the Black Max reside on the top of the bed sides.
Pluses and minuses in all choices.