I could be wrong, but from my understanding you cannot sell the lower ever since you don't have a firearms manufacturers license. So its yours forever.
This is not exactly correct.
1) You
can transfer a homemade lower to another person.
2) You
can transfer it in exchange for money.
3) You
cannot transfer/exchange it
for profit.
Now, how you balance 2 and 3...... *shrugs* good luck getting an answer on that.
The coles notes is that:
If you make a homemade lower, and 3 years from now get bored of it and sell it/transfer to someone, the CFO/RCMP doesn't really care.
If you make 6 lowers in one year, and then transfer them all to other people, you can expect to be asked some very pointed questions about your activities.
Mine were made from solid blocks of aluminum, not 80%.
In so far as registering them:
Mine were verified over the phone with the CFC, and I had to send pictures to the RCMP-SFSS (the same ones outlined in the latest RCMP-SFSS memo) . The criteria for the FCG pocket was the same as is stated in the latest memo released. That was, IIRC, ~8 years ago? So the criteria has been that way for at least that long.
One lower took less than a week to be approved, and the other took 2.5 weeks to be approved (the latter was registered with an upper whereas the former was receiver-only, which may explain the difference in time).