Makes perfect sense.
The code in your initial answer helped solve my problem of computing the FC layer input size, so I will mark it as the solution.
For anyone else reading, note that my first and second code snippets are different in exactly the way described in the thread (sequential vs concatenated), except the FC input size computation is wrong in the first snipped (also described above).  I’ll see about posting a follow-up if I end up using the sequential approach.
Thanks again, @vdw.