Ted has forgotten more about trimming airplanes then I will ever know, so I offer this alternate point of view with caution.
Learned this lesson flying RC sailplanes, if you want to penetrate in the wind you move the CG AFT. Reason is with CG forward in glide you must hold a tick of up elevator, with CG farther forward you need more up - hence it balloons. Move the CG aft and penetration improves - even old floaters like the Olympic can be improved this way.
I only recently encountered similar behavior in a CL model. An somewhat extreme case, my new Joker OTS bird with power on balloons coming into the wind when the CG is forward. With CG aft it does not. I need to measure the tail area & specific CG locations and plug it into Ted's excellent ROT for CG's. My guess is that een the aft CG is forward of what Ted's ROT would suggest.
Does your Stuka exhibit any other habits that could be attributed to CG being out of place? Does it favor turning in one direction versus the other? - that might hint at the elevator adjustment...