Martin and or Elegy (both on this forum very occasionally) are the men to ask, but as far as I recall;

Longer stingers (and shorter headers) move the power further up the rev range.

Dave (Elegy) did suggest putting a small spacer (a couple of cm) between the header and the cylinder, as my racebike pipes (from an RS) were probably designed to rev too much for the NSR cylinders they were attached to.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread