My plugins had not been updated for some time; sorry about that. I have now released a new version of the "KC s2M Pro-rates" plugin with a small but useful improvement.
The plugin now supports multiple Checkout Options in s2Member® shortcodes. As before, every option must use the "modify" type. The plugin processes the individual option shortcodes, not the wrapping multi-option shortcode. Replace each option shortcode with the corresponding shortcode generated by KC s2M Pro-rates, and apply the change carefully.