Who is insuring you while operating the aircraft?
The owner will be covered (for hull loss) under the aircraft insurance while you are operating it, however if you bend the aircraft then the owner's insurance provider will come knocking at your door looking to pass on the liability. Normally this sort of thing, be you an instructor at a flying club, or a CPL at a commercial operation would be covered under employers liability insurance. In the scenario you present above, you are individually liable and need protection in place to mitigate against that. That isn't as easy as it sounds to obtain...