Made my rack today. I will be making a second rack, but I will also add the bathroom paneling to the tops of the shelves in which the tubs sit on. That way I have more of a surface to fasten the heat tape or heat pad too.
I also glued my upright supports in place except in the middle and top level and there I used screws so that if I have difficulty moving the rack or need to move it into a lower room I can adjust the height as needed.