As I tried to find the right (warm) place for my grow kit I found out somewhere maybe perfect (I hope). That is on top of my modem. I've got a temperature around 27 degrees C and it has the exact are size of my grow kit. Has anyone tried this? Anything to write? (before it's too late)

You don't need to heat them...they will grow fine in cooler temperatures and generate heat themselves as they grow. Factoring in the heat they generate, I'd be willing to bet that the temperature of your substrate will surpass 82F, which is what I assume you're shooting for.

Iirc, the 82f was shown to be unnecessary and potentially slightly too high despite research in the 1980s that claimed it to be the ideal temperature. Fwiw, I've fruited cubes in temps anywhere from 60-80f with little trouble.

Higher temperatures simply increase the likelihood that contams will take hold and compete with (or outcompete) your mycelium. If your house is at least in the mid- to upper- 60s F, I wouldn't worry about heating at all.

Good luck with your grow

My home temprature at this time of year vary between 60-80F so that should be fine.
But I've read that for better (faster)growth the temperature should be around 77F is'nt that right?
Forgot to mention the strain which is B+

I'd say that faster is not the same as better

For faster growth, 77 may be preferable to lower temperatures. I wouldn't claim to know authoritatively, personally, as I gave up incubating my bulk sub after my first run(s) (had other uses for the incubator) and don't pay too much attention to the ambient air temperature, as long as I'm comfortable in the room in shorts. The warmer your substrate is, the more susceptible it is to contams.

Personally, when it comes to growing shrooms, I'm in no rush. Things colonize as they do, pin when they're ready and flush as they feel. I'm not too concerned with an extra day or two or three here and there, so I've never really tried to optimize my grows for speed since my first successful run.

For that run, iirc, I had my various substrate tubs in a tub in tub incubator at somewhere between 75-77f and they turned out just fine.As my foci have changed since then, I don't really bother with it.