Bonjour Ludovic: I have always been using panel mount
microphones on my gliders, and they perform just perfectly.
They take up very little panel space, usually less
than 20mm diameter, they are light and unobtrusive
compared to the boom type. Radio communication is absolutely
normal, you only have to raise your voice level when
there's a lot of ambient noise (flying fast with open
ventilation, or high vario volume), otherwise you always
transmit 5/5. They are not suitable for motorgliders,
of course.
Good ones are expensive: 110-150 Euro, but I once made
one myself with the mic capsule extracted from a cheap
handheld mike, and it worked 100% ok.
I would not do without one such microphone now (by
the way, I have two brand new gooseneck microphones
for sale: interested, anyone?)
Cheers,
Flavio