The ornamental design for a mountinghead, as shown and described.
FIG. 1 is a front top perspective view of a mounting head showing my new design;
FIG. 2 is a front elevational view of FIG. 1;
FIG. 3 is a rear elevational view of FIG. 1;
FIG. 4 is a right side elevational view of FIG. 1;
FIG. 5 is a left side elevational view of FIG. 1;
FIG. 6 is a top plan view of FIG. 1;
FIG. 7 is a bottom plan view of FIG. 1; and,
FIG. 8 is a rear bottom perspective view of FIG. 1.
The broken lines shown in the drawings are included for the purpose of illustrating unclaimed portions of the mounting head and form no part of the claimed design.