Mark, not sure whether your thump is the same "high or low" or it's "less" when low.
Oh, okay, so I'm not having your experience, at least in terms of the words I understand and use to describe mine. Not sure yet whether it's the "opposite" experience of yours, "exactly".
What I meant is this: At the higher string height, the Pistoys of course have more room to vibrate. They are louder and the voice of the strings in sustain post-thump ("singing") is much more prominent. That is just generally how gut strings are at a higher playing height.
I like the playability at the lower point, too, but not the sound. I don't understand what you mean when you say your Pistoys sing more a the lower height, I'm assuming you've got them at about 6mm or so. It seems to me your bass would not differ from mine on this bassic point, so I assume I haven't understood what your thought is.