[For 1.6] [Updated] Invitation System

[ajithh]

Hello,
Thanks for the plugin.
I was experimenting with it and have a few doubts / suggestions.
1) Though I have given the option for registered users to only invite members to the group of registered users, still they have to select this only option from the drop down menu . Can it be made so that they need not select the option, but it gets filled automatically?
2) Similarly, it is optional to send the invitation by email. Is there an option to make it mandatory or may be, if I don't want to invite through the system mail, not to show the option?
3) If an email is sent through system mail, how can I have a standard header and body for the mail?
4) Can I set a mandatory value for the expiry period that cannot be changed by the user ?

Thanks in advance,
ajith