Underextrusion PETG

I've been trying to tune my profile for some time now but always end up with underextrusion, I'm running 15mm2/s volume limit and volume tests show I could go over 20. It's Rapid PETG from elegoo. Maybe the print is too big in general and I should move to 0.6mm nozzle? At the top I also seem to require some more cooling, some layers look too hot and melty. Has anyone used the Rapid PETG from elegoo here and maybe has some pointers? Settings: temp 245 bed 80 pa 0.09 flow ratio 0.93 max volum speed 15 60-85% cooling, 6 and 8 sec layer times 10 degrees overhang threshold 100 fan speed