IDG,
Yes you can put in a fixed de-rate, on our 26k aeroplanes you can use derate -1 which is 24k and derate -2 which is 22k.
The Vol 1 says that rated thrust is achieved at a thrust lever position less than the forward stop - ie there are more n1's available if you poke the lever forward.
V1MCG isn't a huge issue, even at 26k it is only around 108-110 knots.
you would have to be pretty light to be using speeds that low.