The Tay engine (F70/100) required a TOGA takeoff every Monday morning to see whether the engine would deliver the required EPR, and therefore thrust, without busting any limit - be it N1, N2, EGT or whatever. If the engine hit any limit before showing the required EPR, a severe engine damage was assumed and a shutdown ensued. This was up to the flight crew; everything beyond this simple monitoring was a job for maintenance.
The difference in thrust during cruise with synchronized N1 was not really noticeable - generally, the rudder trim was set after takeoff with the engines still delivering equal EPR (unsynchronized N1) and did not need to be touched again for the remainder of the flight. May well be though that the tail-mounted engines with their short arm play a role in this; on types like the 744, the situation may be different. The additional drag caused by this is consequently likely negligible.
Last edited by Tu.114; 17th Aug 2013 at 09:35.