I noticed that some presets I had downloaded from Custom Tone could not be imported onto my Stadium XL floor, so I wondered why.
By editing the ".hsp" file that I couldn't import using a basic text editor, I noticed a difference in this value:
"device_id": 2490368,
Whereas the files that work for the Stadium XL have this value:
"device_id": 2490369,
9 instead of 8.
So I modified it, saved it, and miraculously it worked.
There you go, in case it's useful to you...