To tow a four meter glider, briefly, depending on pilot skill, anything from a 2 stroke 1.08 on a beefed up Senior Telemaster to a moderatly power ful G-45- G-62 powered tug.
I have a good article on what is required on my web page

HTTP://www.scalesoaring.net

http://www.scalesoaring.net/tips.html

Go to the Scale Soaring page link, and click on Tech Tips in the left margin. Planes are described in a general way as to attributes. Generally excess power, a stable design, and rugged construction are good attributes.
I have a PDF file link to the JR aerotow on my events calender plus other aerotow events around the country.
http://www.scalesoaring.net/EVENTS.HTM

JD