Did you also consider the QT Halo instead of the Clarity Aloft? They are about 30% less expensive for the same quality. (Or, at least, for the same marketing hype.)
Another mate had a set of earpeices made by a high street hearing aid company, he really rates them!
What I understand is that this is not recommended. Such an earpiece is going to be rather rigid and it's thus virtually impossible to get a good seal. Particularly if you consider the changed circumstances since the imprint was taken: Different temperature, different pressure, different build-up of ear wax... This is not so much a problem for the hearing impaired as they're not looking for sound insulation to a great extent. But it is important in a noisy cockpit environment.
So the foam tips still seem to be the best solution - if you can stand a little pressure in your ear canal, that is. But that pressure, just like the clamping force on a PNR headset, is necessary to create a good seal.
(Note that I have no experience with them, but I am considering getting a set so I've been doing some reading about them.)