My Vstack is perfactly circular , in addition , my application is in a Fw190 cowl , the prop blast would be buffered by the front of the cowl rim , possibly totally buffered based on the blast going both internally thru the cowl and outside the cowl past the carb.
Assuming it was designed by greater minds , I guess my best bet is to cut an opening for it , use it and see how the engine performs .