Why not try simply:
$SiteOriginOptions="a:14:{s:10:"post-types";a:2:{i:0;s:4:"page";i:1;s:4:"post";}s:10:"title-html";s:39:"<h3 class="widget-title">{{title}}</h3>";s:16:"add-widget-class";b:1;s:15:"bundled-widgets";b:0;s:19:"recommended-widgets";b:1;s:10:"responsive";b:1;s:13:"tablet-layout";b:1;s:12:"tablet-width";i:991;s:12:"mobile-width";i:480;s:13:"margin-bottom";i:30;s:22:"margin-bottom-last-row";b:0;s:12:"margin-sides";i:30;s:20:"full-width-container";s:4:"body";s:12:"copy-content";b:1;}";
update_option('siteorigin_panels_settings', $SiteOriginOption);
Also, you may want to set a flag to say the options have been initiated so the user can change them later and not have them overridden whenever they activate a plugin.