I was going to say the same as
Tinstaafl.
The transonic regime is analogous to the planing hull scenario.
From a
mechanics of flight point of view, I can imagine some interesting things happen if you are climbing at a speed which corresponds to the neutrally speed stable point at the bottom of the drag polar i.e., V_md. In this case, how you reduce the power as you approach the target altitude is critical as you may or may not wind up on either side of V_md whereupon speed stability is qualitatively different. It tends not to be a problem in commercial jets because we don't climb at speeds approaching V_md. Au contraire, I suppose in gliding, its
all about V_md!
From an
aerodynamic point of view it doesn't get any more difficult than unsteady (transonic) aerodynamics and without doing the testing, I wouldn't like to comment about the potential hysteretic effects
FullWings mentions but essentially unless you've somehow sustained a qualitatively different flowfield, in the
steady state case, there should be a unique value of velocity for the given thrust. My summation would be that in the world of in-flight Reynolds numbers, turbulence will destroy any laminar type effects that you'd prefer to persist.
OVERTALK
The fact you only saw a miserable 12kts as opposed to 15kts, is surely a reflection on your good airmanship and your view on where its sensible to keep the CG.
My $0.02.
