Leaders of Hollywood’s two biggest performer unions have set a key meeting for Dec. 11-12 to prep what could be a final proposal for merging the Screen Actors Guild and the American Federation of Television & Radio Artists.

Spokespeople for SAG and AFTRA didn’t respond to a request for comment about the meeting, which would be the fourth formal confab of the Group for One Union — consisting of members from the SAG Merger Task Force and the AFTRA New Union Committee. The G1, with six workgroups, has since June been hammering out details such as a constitution, financing and dues with the target of presenting final proposals to the SAG and AFTRA boards in January.

Other than touting the meetings as productive, the unions have disclosed only general details about the substance of discusssions.

Proponents have argued that a combined union would be more powerful and remove jurisdictional overlaps. Opponents have contended that the new union should be for actors only but SAG voters have been backing pro-merger candidates overwhelmingly in recent elections.

Should the proposal be approved by the national boards, members could be asked to OK the merger in a contest that would require 60% of those voting in each union to approve. SAG currently has about 120,000 members while AFTRA has about 70,000 with about 45,000 performers belonging to both unions.

SAG members turned down merger votes in 1999 and 2003.