How to select earmold vent size

Dear everybody!
I currently use two Phonak Savia 311 for 5 years. My right earmold’vent is 2mm, but I always feel occlusion. It bothers me so much.

this is my audiogram:
Left : 250:60; 500: 70; 1000:75; 2000:65; 4000:60; 8000:50 ;vent 1.5
Right: 250:25; 500: 40; 1000:70; 2000:65; 4000:55; 8000:50 ; vent 2.0

Should I use Open Fitting for right ear? Please help me! Thank u very much!