In web/plugin/gateway/gammu/config.php on line 13, the code $plugin_config['gammu']['dlr'] = TRUE; sets delivery reports to be on by default. Using gammu in files mode, the d extension suffix seems to take precedence over the config variable deliveryreport = no. This slows large SMS sends to a crawl.
What is the benefit of delivery reports by default? Most SMS apps in regular phones have them turned off. If you could expose a setting to disable them in the SMSC config for gammu, that would be appreciated.