Do you know what size hole/threads you used?The new mount is round tubing, and on initial inspection is super sturdy feeling, but the more you tighten the more it leans in toward the water. At least with a rimmed tank, maybe its different when you have a rimless tank? But the weight of arm + light makes it fall completely forward.
So i referenced the "directions", and it shows installation screws on the inside, but that would leave the excess tubing going into the water...
But with the screws against the glass, it feels sturdy. So I had the husband redrill and tap two holes on the opposite side where it was blank.
So now its mounted up and looks good, feels sturdy. Took hubs less than 5 minutes.