Alex here is a nose release sold by Hobby Lobby that would work fine turned around and mounted where needed. All of my towing has been on both ends of glider aerotow and my releases have aways been just simple pelican hooks I copied from full scale releases and made of bits of wire and brass soldered and actuated with a servo. The two attached pictures will give you an idea as to how it works, simple and reliable. You release could be as simple as two small eyescrews with a bit of 256 rod running through the eyescrews and the other end of the rod attached to a servo. when the servo withdrew the rod a keyring between the eyescrews with the cord tied to it would be released.

http://www.hobby-lobby.com/aero-tow_...e_535_prd1.htm

John