How hot should NIMHs get?

[R.C.Hole]

Anybody have an idea how hot NIMHs should get?
I'm running a D4 with a 5700kv brushless (approx 6T) on a 7.2v 4000mAh pack and depending on the surface I'm running on I can burn myself on it (even worse with my old brushed 15T).
I only bash for now and its the only pack I've got so i don't have experience with lots of batteries.
Also does anyone know a max safe discharge rate (before you start to damage them) all Lipos have it marked on them but I can't find any info for NIMHs;

Any help would be great.