Erowid lists 10mg as a 'light' sublingual dose.
It is late now and I do not remember where I read it, so take it with a grain of salt, but I seem to recall that 5-MeO-DMT can be overdosed, and such an event results in respiratory arrest.
So, remember that not only you are dealing with (according to a lot of experienced psychonauts) the most powerful psychedelic on the galaxy, you *might* also (pending confirmation of said information -- I did quickly utfse now and could not find any information on 5MeO overdosing) physically die.
There does not seem to be a lot of information on sublingual administration.
Explore safely.
This is the time to really find out who you are and enjoy every moment you have. Take advantage of it.