I did use top Eb's in the Solo Cornets, yes! BUT,,,,,, it is still reachable by many many cornet players and indeed a top Eb isn't really that high, not unless ur a 3rd Cornet. The argument of the Euph has nothing to do with players getting the notes, but the physics of the instrument does not allow satisfactory production in 99% of cases, as I said if u're gonna go down that low and refuse to change the vocings, then u're better off with an Eb Bass or even a Bass Trombone.
There is something to be said of the quaility of the player to reach down to bottom E (Satisfactory in the context of a performance) It's a ll very well practicing low low notes in the bandroom on your own, but in performance, things start to go funny.
I wouln't say I was dead against the bottom E going in, and without the score, one cannot be totally sure, you might get away with it, but my instinct tells me no - especially in quartet writing!!! A bottom G or an F will have some Euph players 'grumbling' around down there in atempt to find the right timbre to produce a satisfactory note.
Much of it depends on your voice leading, but as I said if your approaching the Bottom E by leap (and it forms the Tonic of the chord) one would be best to write the Bottom E up an octave (other parts permitting and may need changing??)
But do take it to ur band and get them to run ti, you'll be able to make your own informed decision! :wink: