Not really. By having another letter, you get 25 times the number of
possible combinations. That should last for a while.

Actually, they have C-Fxxx C-Gxxx C-Ixxx (for ultralights). This gives three
times more combinations. While other letter combinations are available, some
are already in use (countries such as Chile CC, Cuba CU, Nauru C2, Morocco
CN, Mozambique C9, Uruguay Cx). See
http://www.lentoturvallisuushallinto...rcraftnational for a list (note
that Canada is missing the CG... probably a typo).