I'm not an attorney but I am a Connecticut resident and I accomplished a rather difficult sale of a boat here three years ago.
First of all, it is the buyer's responsibility to go the DMV and present the signed bill of sale portion of your registration certificate. I don't think the DMV will feel responsible for enforcing any conditions that you might impose on another Bill of Sale that you created.
Once they see their Bill of Sale signed by you, they will calculate the sales tax and registration charges, collect whatever is due from the new owner and re-issue your boat's numbers to the new owner. (In CT, the numbers stay with the boat.)
From my experience, you need to settle any differences you have with the buyer before you hand over the signed DMV Bill of Sale. I'm quite sure that the DMV will not act as your agent to enforce other conditions that you may have set on the sale.
You can try calling CT DMV but you won't get very far. You can visit one of their offices to ask, but be prepared to take a number and wait, sometimes as much as several hours.
Best I can do for you. Perhaps someone else here knows more about Connecticut DMV regulations.
Bill