David Tyler crossed several oceans without boom gallows (see above) for his wingsails before he put his massive new junk sail on. I don't think he has a gallow (?) on that either.
My Sunbird 32 had gallows (well, one for the main, and a crutch for the foresail). When we sold her and got Paradox (ex Freedom 39 Pilothouse Schooner) I really missed them and had some made. The main is pretty heavy, so I felt that a gallow/s was/were essential anyway, and it's become a useful and secure vertical grab point each side of the cockpit.
On the Sunbird we had situations in which the main would swing harshly from side to side - motoring into rolly rivers, at anchor sometimes. Lashing the boom as described above works but can take time. I was always glad and sometimes relieved to be able to simply lower the boom with the running lazyjacks into the gallows.