I moved a Y-flyer out of a potato  barn back in the 70's thourgh a regular door and down some steps.  The one thing I remember about that operation is build a boat behind a garage door. The other "one" thing I remember is  bring more guys. I did it with two of us. It needed more.  Today I'd also specify "young guys".

 I found it difficult to carry my dory by the ends upside down even with one guy on each end...it kept wanting to roll right side up (I guess it's good a sailboat is self righting!).  It was easier with people on the sides whether upside down or right side up.

Four people, one on the bow, one on the stern, boat on edge with third person steadying  the boat by the dagger board trunk, fourth and person outside the door. As you go out the door # three hands off to # four and down the steps they go. Or you can wait for the rising sea fevel and float it out!!! SEEYA Jack

Jack-  Thanks for the great suggestion on using the centerboard trunk.  I think I will make a piece that inserts in the trunk and has a handle of some sort.  It will come out.....  Thanks again.   Dave