Created attachment 4422 fix-border-width-to-be-the-same-as-the-other-plugins.patch The other panels all add a small border. This patch makes the plugin match that behaviour. Actually, most other panel plugins also don't set the size manually (see PBAR_THICKNESS), so there's a (though only slightly noticeable) difference too, but I didn't want to change that with this patch.
Thanks for the patch, this will be included in the next version 1.0.0 which I will release soon.