Ken Freeman wrote - >>Turning the bar 90 degrees causes the head tube to drop, steepening the head tube measurement.<<
Every head angle has a correct fork rake. The top tube will drop only if the fork rake is too short for the head angle. It will also rise if the fork rake is too great for the head angle.
The relationship for no movement is: Fork Rake = Wheel Rad (1- sin a) / cos a,
Where a is the head angle.
Seat angles for team bikes at Ilkeston were not quoted, but the dimension used was afterbracket or set back as Norris Lockley outlined in his post.
Mike Mullett
Reading UK