FIG. 1 is a perspective view of a support structure for a stairlift chair showing my design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a perspective view thereof, the broken lines showing a backrest, armrests, a seat pan, and footrest of a stairlift chair illustrate environmental structure to which the support structure is installed and the positioning of the support structure in relation to other components of the stairlift chair, and form no part of the claimed design;
FIG. 9 is a back view thereof, the broken lines showing a backrest, armrests, a seat pan, and footrest of a stairlift chair illustrate environmental structure to which the support structure is installed and the positioning of the support structure in relation to other components of the stairlift chair, and form no part of the claimed design; and,
FIG. 10 is a left side view thereof, the broken lines showing a backrest, armrests, a seat pan, and footrest of a stairlift chair illustrate environmental structure to which the support structure is installed and the positioning of the support structure in relation to other components of the stairlift chair, and form no part of the claimed design.