ORIGINAL: qweedqwag
Right thrust is set by the firewall not the nose ring.
And good manufacturers then repeat that side thrust in the nose ring so you have an equal gap between spinner and cowl all the way round.
As for the extra, the cowl on my GP extra is completely open at the front. Mates Goldberg extra was the same. See this photo of Patty Wagstaffs extra. Completely open behind the spinner.