If pairings are announced, tables found, asteroids and deployment completed and then the 60 min round starts there is really no excuse not to finish that game. I've played 17 tourney games of this format and finished every one, and seen maybe 15% go to time on other tables.
This depends entirely on the players present and is outside your control. In the two small Store Championships I went to, both used 75 minute rounds and over half the games went to time. My experience may not be typical, but it is not that uncommon for games to go to time even at 75 minutes - especially if someone is using MoV to their advantage and slow playing (which is technically against the rules but impossible to determine and enforce).
I know your principle reason for championing 75 min rounds is on the basis of leveling the natural advantage of fatties and the 'all or nothing' MOV system, but I don't really believe that round length is directly related to that problem. Does the data you've been crunching record the round length of the tourneys to see if there is a higher percentage of 2 ship/fattie builds winning 60 min round events?
Edited by Rauhughes