Hi broadblues,
I use HD-REC with a velocity-sensitive MIDI controller and it records different volumes depending on the velocity but the maximum volume seems to be 77 (out of 127). I never quite figured out why, but coincidentally creating new notes by clicking on the piano roll with the mouse also makes a note at volume 77. I tested the same controller on GarageBand on a friend's Mac and it does go up to the maximum 127, so it's not a setting on the controller. I have a second keyboard which is not velocity-sensitive and HD-REC records 127 on every note.
It does seem there is a maximum or default velocity setting HD-REC, but I can't find it.