Keep in mind that along with the decalage change you'll most likely need to move the CG back to see the improvement. Otherwise if you leave the CG where it was you'll have to add up trim to achieve normal flight and the effective stabilizer angle will end up right back where it was and you'll still have the strong climbing tendency.

It's the CG location that is the real culprit in all this. You COULD have just moved it and added down trim to effectively do the same thing as cutting and gluing the stabilizer on at the new angle.