The ACBL Alert Chart states (line 1) that:
Natural Calls Not Specifically Noted [with] Unusual strength, shape, etc
must be alerted. Both your 1C and 1D opening bids imply unusual strength and shape requirements, and so must be alerted.
In addition the ACBL Alert Procedures guide states:
Systems that may be Fundamentally Unfamiliar to the Opponents
When you play a system structured along different agreements than [those described in the preceding paragraph], you should draw the opponents’ attention to your convention card before the round begins. In short, if you play a system that most players would not immediately recognize ... or one the opponents may wish to discuss before the auction begins ...),
you are required to pre-Alert the opponents.
In my opinion your 1C and 1D openings are such a system agreement, and I would expect a pre-alert along the lines of:
- All non-forcing openings intending to rebid 1NT or 2NT are opened with 1C.
- Unbalanced hands of the same ranges with no 5+ Major or Club suit are opened 1D.
I am adamant on the pre-alert because the very advantage that you receive from this agreement is one that the opponents may wish to mitigate by modifying their defenses for.
I can easily conceive of defending your 1C opening as a 15-19 NT, and competing at the 2 level with our 1NT defense. This will interfere with your ability to distinguish between your 15-17 and 18-19 NT openings, and reduce your game bidding accuracy on 3NT and 4M contracts. I would enjoy seeing how that works out for you and partner.
TANSTAAFL - There Ain't No Such Thing As A Free Lunch.