Thanks for the replies everyone. A little background to my query is called for, as you have all gone to a lot of trouble to reply.
My old airline of countless years ago operated out of several Pacific atolls. The airstrips were built from compacted coral and were often rough as guts. The aircraft really took a beating on take off and landing. We used reduced thrust because invariably we were very light, and the speeds were low anyway.
The boss chief pilot decided that due to the rough runways it would be better if we got airborne with minimum take off run - understandably. So he put out a directive that we were not to use reduced (assumed temperature) thrust but instead go for full power. 2.18 EPR in those days. But then he got the idea from somewhere that if using full thrust you must therefore also use the V speeds for the performance limiting weight which required full thrust.
Yes - you guessed it. We were now holding the aircraft on the ground (and getting the bejeezus belted out of the poor 737) for anything up to 15 knots higher than previously.
I queried this and was told that too bad, that was the legal way to do it - ie use V speeds for theoretical max performance limiting weight. It didn't make sense then and it doesn't make sense now. But there are operators who still do it that way when lighter than the performance limiting weight.