The ornamental design for a wallboardinstallation brace, shown and described.
FIG. 1 is a side elevation perspective view taken from the top and left side of a wallboard installation brace showing my new design;
FIG. 2 is a side elevation bottom plan perspective view thereof, it being understood that left and right side views thereof are mirror images of one another;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a right side elevation view thereof:
FIG. 5 is an end view thereof;
FIG. 6 is an opposite end view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is an environmental, side perspective view thereof with the broken lines showing a wall stud, wall header, section of wall and the wallboard brace hole being for the purposes of illustrating environment and forming no part of the claimed design.