I aerotow with a DR400/180R and have about 50hrs (including most of my PPL) done on a PA28.
Keeping the stick back on a PA28 for that long is uncomfortable at best. You should be able to feel the aircraft starting to unstick. If you're on a tarmac runway, start with the stick in the middle and "check" back on the yoke at 60ish kts.
Brief for aerotowing in the DR400 is start with the stick on the back stop and as it starts to unstick, relax the back pressure so it flies off in a 3 point attitude - then once accelerated in ground effect to climb speed ease into the climb.
Enjoy the robin, they're lovely.