If I' m not mistaken the Nitro website doesn' t recommend a choke tighter than .665
I would be hesitant about the .655 Ventilator. It could be that you are getting too tight and need to open up the choke some. I patterned my 24" Nova the other day with the factory Modified and Full chokes and was very impressed with the Remington Hevi-Shot. If I can ever get some time again I' ll photo and post results.
MS, do the Remington chokes come to fit a Benelli? or have you had your Nova refitted for RemChokes?
Ah, here it is (I printed it out and it' s laying on my desk.)
Tighter chokes than .665" do not improve pattern percentages to any extent and in fact begin to produce more open patterns.
Their tightest test patterns were with the NEW HEVI-SHOT (.675" ) at 94%