Couturier mellophone

Last year I wanted to get me a new instrument. Window-shopping for trumpets is no fun - they all look the same. But then I came across one that is different: a Couturier Conical Bore Bb/A Trumpet. I was really fascinated: conical bore, takes a cornet mouthpiece, and especially the Bb-to-A switch valve... But when it came, somehow we did not click. I cannot explain it well, I just did not like it enough (maybe just not enough to pay $700) - so it went back.
Around that time I put in an eBay search filter for "Couturier," and one day a mellophone in Eb came up. Now if the trumpet is unusual, this thing's freak factor is off the scale. I could not resist. It cost me $100 including shipping, and I spent 75 more fixing it: frozen slide, broken water key, mouthpiece replating. I think the repair people were rather puzzled as to who would want an instrument like that and why.
One thing with the Couturier instruments - conical bore means none but the tuning slide are removable. OTOH, the inclined design means all the oil, spit, and grease goes directly into the slides and accumulates there. I had to soak and clean it out three times before it lost that godawful smell; the cleaning was rather tricky too - getting the snake into the slides from inside the pistons etc. Now it's perfectly playable and indeed rather nice. The only problem is it's missing a case. My wife tossed out the original case for it stank out the house and was really beyond salvaging. The french horn cases are expensive and don't fit too well.

So, how does it play? I think it plays great. It does sound like a horn - maybe not exactly, but much more like a horn than an oversized Eb trumpet. It could be the overall "horn" shape and the conical bore, but also the mouthpiece, which is a lot closer to the horn V-shape than to a regular trumpet mouthpiece. Above the staff the notes get rather tricky - G is OK, A is difficult.
I wasn't sure what to play on it, though. I did a two trumpets/mellophone/baritone arrangement of Bach's Durch Adam's Fall and practiced the horn line for a bit. Now I am thinking it will work great with the real horn repertoire; I think I'll try Mozart's horn concertos.
Mozart's manuscript contains bizarre scatological comments addressed to the horn player - can you beat that?