I don't see where you came up with those numbers but I'd like to defer that to a GCS configuration page that makes sure the orbit radius and other numbers for FW are _al_l consistent rather than putting those kind of checks into manual control.  If that math should should be done to massage the radius is should be done in the fixed wing follower.

This patch essentially takes the radius from 0 (previous behavior) to user configurable so while I don't dispute more could be done, it seems like a step forward.