Yes, definitely a bad idea. Use 8va. .... brackets instead when you want to
send everything up an octave like that. It was fine for _you_ because you wrote
it and knew what you wanted anyway, but it would have probably been confusing
for anyone else who had to read it, at least at initial glance.
Anyway, _most_ of the time you shouldn't need to do any such octave shifts --
it's only at the very extreme upper end of the instrumental register (and
sometimes lower, e.g. on piano) that you would bother.