The ornamental design for an extendabletower mount, as shown and described.
FIG. 1 is a front elevational view of the extendable tower mount showing my new design.
FIG. 2 is a side sectional view thereof taken about the line of FIG. 1.
FIG. 3 is a detailed sectional view taken about the circle of FIG. 2.
FIG. 4 is a bottom plan view thereof.
FIG. 5 is a front elevational view thereof shown in an extended orientation.
FIG. 6 is a three-dimensional exploded isometric view thereof; and,
FIG. 7 is a detailed three-dimensional isometric view taken about the circle of FIG. 6.
The solid angular crosshatched lines shown in views of FIG. 2 and FIG. 3 are there representing parts of the cross section area and do not form any part of the claimed design.