Frankly, I don't really understand what the problem is. I believe to understand that you have wing and stab at the same incidence (that is zero decalage) and that you can't change that easily.

Now, if you observe (on the one hand) that the model is fine in level flight and (on the other hand) it pitches up into a hover when a loop is tried, then I think it's balanced quite rearward (to match zero decalage) and it's actually unstable. So when it gets over a certain point (only a bit pitch up) the pitching-up is self-energizing. I wouldn't think that could be corrected with down thrust, but only with a more forward C/G.

The reason why I think so is that a Telemaster has flat-bottom wings (and even stab, for that matter) which have a strong down-pitching moment not depending on lift but on airspeed squared. You might have found a "sweet spot" (by chance) for level flight where all is balanced. At lower speed (take-off, loop) the down-pitching moment is lower and the airplane rears up.

If that is the case, more decalage (and the corresponding more forward balance) is mandatory. Since the stab is fixed I would just think of shimming the wing, regardless of bolted or strapped on. Just my thoughts...