It's not forbidden to do the two together.
In certain companies, they routinely do this, as this will preserve engine life. Improved climb allows to assume even hotter temps.
And they also add derate on that!
Just make sure you have the correct tables. The mechanism in itself works pretty well.
On some runways, on the 300, using flaps one is even less restricting, so you'll end up eating a lot of runway... fells great to look like a 747!
(slightly less if you have to abort...) 
LEM