I look forward to the results Chaplin!
Here is a thread with the specs on the K&N
Stellings & Hellings w/ K&N airflow
Do a search on 'K&N flow'. Lots of information.
I would think that the effect would be worse on a single carb motor because of the size of the carbs.
I currently have one of the big 14" x 3" K&N air cleaners and a stub stack. All of it is coming off for a Stellings and a good ole turkey pan. Since I have tons of hood clearence I am going to stack two of them for every day use. This will flow as much as my carb does so I am not expecting much if any seat of the pants feel between the two.
By the way the Xtreem lids do come in a 9" (nothing smaller) but I know a number of guys that use them on top of the stelling cleaner for daily use and clame there is a groove where the filter fits nicely into. Lid is about .8" larger in diameter than the filter. The Xtreem lid flows 100 CFM. Accordind to K&N.
Rick