Your friends are correct, you should open the airbrakes. You only need
them until you have passed the point where the tow plane started its
takeoff roll.

You have probably noted that you are consistently dropping the same
wing. It is a result of turbulence from the tow plane. Mark where the
tow plane began its takeoff roll and anticipate the turbulence as you
approach this point. Also, get the tail off the ground as soon as
possible to lower your angle of attack and enliven your ailerons.

Be sure to add a checklist item to your take off... to visually check
that the spoilers are not deployed after you break ground. You may
also want to keep a finger or two on the aft side of the spoiler
handle until you've gotten used to closing the spoilers and locking
them with each take off.

Hope this helps.

Chris OC