I didn't push it in at all, there wasn't any room for that - I simply filed it off together with the surrounding plastic.
If you have another drive than the one in the video you can't slavishly follow the steps described there anyway - just let the head go to track 0 and mark its position, then power down the drive, push the head all the way to the physical stop by hand, and you can measure how much material you'll have to remove. You need a total clearance of 2.117 mm below track 0 which is more than it sounds like
Then you can just turn the drive around and look where exactly the head is hitting against the chassis, that's where you'll have to file off some stuff. On my drive I had to file stuff off both from the drive chassis and from the head assembly, in about four places, and I also had to move the stepper motor itself which of course totally dealigns the drive. And in the end, when the head went as far as it needed to in an empty drive, I still had to push down some kind of metal sleeve around the lower magnetic head because it hit against the floppy disk's own sleeve. Just be careful and stay away from the upper head as much as you can. And if you have to remove any locked screws, it might make sense to lock them again with a bit of lacquer (or with a good amount of ink from an Edding pen).