Blockbandmusic

Does anyone have any experience arranging/composing for this instrument? There is surprisingly almost no information about it. I would like to get an idea of its range. As I understand it, the marching French Horn is basically a baritone in Bb with a French Horn mouthpiece. That being the case, I imagine that it would have the same range as a Baritone playing as low E natural 2 (E natural below the bass clef). What's generally consider to be the top of its range? Here's the most important part of my question though. How does it transpose? If the marching French plays a concert Eb right above the bass clef does it correspond to the F in the lowest space of the treble clef or the top line? With the instrument having such a low range I can't fathom that a ton of its range would be all ledger lines below the treble clef. That would be the case if concert Eb was transposed to the F at the bottom of the treble clef staff.