I tried posi and philips type screw drivers, had the right size in both types, these screws were tight with a capital T.
Glad you didn't have any trouble carlos, I wasn't expecting any, but thats the way things go. Maybe yours had been out before or you had the later screw type, either way the stubord screws I had wouldn't budge regardless.
The slot I cut enabled me to use a large flat screwdriver which gave much more purchase than possible with the cross head.
I'm thinking if I ever have to do that job again then an impact driver (used with caution) would be the best way to go, sods law I couldn't find mine when I needed it...