Parametric Speed Tower with Slic3r G-code generation

A speed tower in OpenSCAD, parametric, you can select speed range and step and feature size.

This OpenSCAD code prints the G-code for Slic3r, clean up the ECHO: prefix and the "" quotes and paste the code into custom G-code "Before Layer change":
{if layer_z >= 1.5 && layer_z < 2.5}M220 S{10*100.0/perimeter_speed}{endif}
{if layer_z >= 7.9 && layer_z < 8.9}M220 S{14*100.0/perimeter_speed}{endif}

Unlike the temperature tower, there is no G-code to set speed, only the speed multiplier. Thi