Beware that according to Costello, thic coverage is really for you. If
you let another pilot fly your plane, they will fix it for you, then go
after the other pilot to reclaim the loss. The other pilot needs to
have his own coverage to be able to fly your ship.

Correct. This is called subrogation. The borrowing/renting pilot really
needs his own renters insurance to protect himself - see
http://www.aopaia.com/index.cfm?parm1=Renters%20FAQ

Tony V.