Just triple click to select all, and set your value by hand. If you use MCCC, you can use MC CAS to set the feet to a specific size - no command line needed.
I know I'm a little late to this party (having come by this version of height sliders by way of TurboDriver not being able to support the (working!) feet method of height sliders, and I saw your comment. And #2 is consistency, as you can't just memorize a height number for each sim like you can with this mod. It would be too much of a hassle to go into CAS every time. I use this mod for white I screenshot my story, and whenever I use a pose, I need to revert the sims back to default height so that the pose lines up well, then put them back to their normal heights when I'm done posing and go back to using in-game animations. #1, Having to go into CAS to change the heights. For me, this mod doesn't work for two reasons.