https://jakearchibald.github.io/svgomg/
I've found this very handy little online tool for shrinking SVG files that you might be interested in. From my experiments I've found you can easily shave off half of the filesize of simpler vectors such as flat shaded company logos, although it's not as effective on more complex designs with a variety of shapes and gradients. As an example, I've managed to shrink the
GTPlanet logo vector from 16kb to 10kb, enough to use it in GTS through the decal importer. You can download the optimised logo
here and give it a shot if you'd like.
One thing of note: by default, the tool will only tell you the compressed filesize of the vector, which is not relevant as the GTS decal importer only cares about the uncompressed filesize (afaik). To fix this, simply uncheck the "Compare gzipped" option on the right.