Yes it is, I think it would be done by adding these lines to the config files respective of your sites...
in site1.sitename.com_config.php:
define('HTTP_SERVER', 'https://site1.sitename.com');
in the file site2.sitename.com_config.php:
define('HTTP_SERVER', 'http://site2.sitename.com');
This means that every single pages of site1 will have an SLL link (not only the secure sections cart, payment, profile...)
I hope this answer your question.




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