hp dv6 3xxx - ati 5470 + intel screen blinking

Hello everybody! I need help.
Recently I updated my hp dv6 3122sl to win8. Now, obviously the drivers provided by microsoft didn't work, so I installed the softpaq by hp in this order
1. sp52351 for intel hd graphics (1st gen)
2. sp50640 for my ati radeon 5470 (it's important to set compatibility with windows 7 for this one)
and now the switching is working fine.
However there's a big big problem. The screen flickers 3-4 times at startup and shutdown if I enable fastboot from the control panel, and it's so annoying that I disabled it, sadly.
I tried to update drivers, using custom drivers by leshcat and later official drivers by ati (13.1 for example, which I installed over the hp ones), and the they -more or less- worked, because I could use the fastboot smoothly... but my pc had several thermal shutdowns since I installed other drivers!
So I switched back to the old sp52351 and sp50640.

There it is my question: Does anyone of you (maybe with intel+ati 5470) have flickers at startup and shutdowns?
If yes, is there a solution or any way to update drivers without make my laptop blow up?

Thank you!