The ladder drill is terrific. Before each round in addition, I put some uphill and downhill to the edge of the green. No hole, so you are not concerned with line. On all puts I settle on line then my only thought is speed, speed...speed.

I take into account on uphill and downhill puts an illusion that I have only heard Dave Pelz address. Because you are viewing the line from 5.5 to 6 ft above the putting surface, puts of the same distance appear either closer to you for an uphill put or further away on a downhill one. This is because of the slant range in your vision to the hole.

Except on very long puts, no one should miss the line by more than three feet or so. It is easy to miss the speed by twice that. A six foot downhill put can be murder under pressure. So my advise is to concentrate on speed and feel, line being secondary.

I recently made a change from resting my club on the ground at address to hovering it fractionally above. This made sense to me because your practice strokes are very lightly brushing the ground or just missing it. I have found that in my case the small lift in the club must have been causing a little change in alignment and that my already good putting is better for it.
Cheers, Bob