The tailwheel does not impact the aerobatic certification.
You are right that some conversions can have impact though ...
A 150 hp engine conversion would likely negate the aerobatic certification. Im sure others are more familiar with the history, so they may correct me on the following...Only the k models retain the rating. As I understand it they skipped the k model when they listed the models that lost the certification in the STC - just a chance oversight). This doesn't mean the other models aren't capable of aerobatics...it was likely not tested for aerobatics by the STC owners at all.
