[kyran]

The nice thing with the fixed length look is that it gives a sort of step sequencer feel to the drum roll.
The idea is that if note length is really that essential, you’re better off using the piano roll anyway.
If you see the drum roll as some sort of step sequencer, then the notes should just send note on messages.
You could perhaps create seperate note off “notes” to allow note lengths to be entered or choke groups to be emulated (think renoise).

Again the idea is that if you should use the envelopes of your drum plugin, or the piano roll if you really need to tweak the note length on every note.