Does anyone know the correct timing for a 1.6 CVH at around 5000 rpm?

Haynes gives 12 deg for 800 rpm but I also wanted to check it higher up the range.

i've been told 32-34 deg. I also read i think that over about 3000 rpm it stays pretty constant, is this right?

Any advice appreciated (destroyed 3 pistons already due to incorrect timing!!)