Where must the glider tow line connection be?
It needs to go just under the tip of the nose to have any chance.  This connection is equivalent to the thrust line of an engine, except that because the connection isn't rigid, the longitudinal location matters; the farther forward, the more stable (if the attachment is rigid, like an engine/propeller, it doesn't matter whether the thrusting component is forward or aft, from a stability perspective).
Probably most normal gliders hook up at the nose but a lot of them have hooks near the center of gravity underneath to facilitate winch launching, and when used for aerotow these are less stable and somewhat of a handful to fly for an inexperienced pilot, especially on crosswind takeoffs.
You will have to set the horizontal tail to apply enough trimming force to overpower the nose down component of the pull of the tow line, that is, more nose-up trim than necessary for free flight.
You will find that because the thrust line is more or less concentric with the roll axis, there is not much you can do for roll stability and will be stuck with whatever inherent stability is there from the dihedral effect of the turned up wingtips. Connecting the tow line to each wing tip will not help with roll, since the two lines still run to a single attachment (until you get the angle of the tow line to the longitudinal axis high enough that the &quot;Y&quot; connection is influencing roll, but the thing may still just arc down into the ground anyway), and connecting that far aft will make you completely dependent on the glider's inherent pitch stability and damping.
My prediction is that as is, whether you hook it at the nose or the wing tips, it will go all over the place, than crash, and to get it to just kite along smoothly behind while on tow, you will need a lot of wing dihedral, similar to a 2-control model.