The ornamental design for a weightscaleassembly with side rails, as shown and described.
FIG. 1 is a front view of the present weight scale assembly with side rails design;
FIG. 2 is a rear view of the present weight scale assembly with side rails design;
FIG. 3 is a left side view of the present weight scale assembly with side rails design;
FIG. 4 is a right side view of the present weight scale assembly with side rails design;
FIG. 5 is a top view of the present weight scale assembly with side rails design;
FIG. 6 is a bottom view of the present weight scale assembly with side rails design, and;
FIG. 7 is a perspective view of the present weight scale assembly with side rails design; and,
FIG. 8 is an enlarged view of the display of the present weight scale assembly with side rails design.
The broken line showing of structural features is included for the purpose of illustrating non-claimed subject matter and forms no part of the claimed design.