Please, quote your source for where a true hammerhead requires ANY throttle work for the maneuver itself (not the portion where you reduce throttle after the fact to manage airspeed).
Williams, Neil (2003) [First published 1975]. Aerobatics. Marlborough, UK: Crowood Press. ISBN 9780950454306.
" ... we apply the rudder as the speed falls through 50 knots and we apply about half rudder quite smartly, at the same time throttling back to half power."
" On some aeroplanes, which have a large and powerful engine, and a short fuselage and span, if the power is left on... the aircraft will roll uncontrollably."
Neil Williams taught himself aerobatics in a Tiger Moth. My dad had a Tiger Moth. Here's an old picture. He's taking off from the glider museum in Elmira NY where he gave a talk on flying wing design along with Rudy Opitz, Karl Nickel, Paul McCready and others. My dad learned about flying wing design from Reimar Horton and talked Reimar into writing the book "Nurflugel". The B2 design team bought 7 copies.
Photo Credit Douglas Bullard
