Thx for all the answars!
I understand that it is not good to make a 3,7 or 4,0 out of my 2,9.
It is better to use a 4,0, but in Denmark is it not possible, because of the tax I have to pay about 60.000 $. So I can´t use any of them, but it is very interesting any way.
I think I have to...