Picking six planes from my hanger and comparing their tendency to yaw left when going vertical.
Plane #1 is a Hanger Nine Ultra Stick Lite. Its fore section is horizontally symmetrical. It suffers almost no left yaw when going vertical.
Plane #2 is a Seagull Spacewalker II. Its fore section is significantly horizontally asymmetrical having a prop shaft near the top of the cowl and an inverted engine completely within the cowl. It suffers significant left yaw when going vertical.
Plane #3 is a Yak 54 (28cc powered). It of course has a round cowl and suffers hardly any left yaw when going vertical.
Plane #4 is an Akrobat II (33cc powered). Like the Spacewalker, it has a prop shaft at the top of the cowl that completely encloses and inverted engine. It suffers considerable left yaw when going vertical. Note: otherwise it is my best flying plane. It will knife edge from horizon to horizon with ease with very little in the way of roll or pitch couple.
Plane #5 is a self designed 35cc with a round cowl. It suffers little to no left yaw when going vertical.
Plane #6 is a Hanger 9 PT-19. It of course has a high engine shaft on a cowl that completely encloses an inverted engine. It as well suffers a good bit of yaw when going vertical.
I of course don't know if six planes are evidence for anything. Perhaps if others compared their planes and offer the observations relative to left yaw when going vertical and if the fore sections are horizontally symmetrical or asymmetrical.
I don't mean to imply that there is absolutely no left yaw on the three with horizontally symmetrical fore sections. Actually none are perfectly symmetrical. The stick has a jug that hangs down and the two others have spark plug cables that hang beneath the round cowls.