No it would not have been better if I had posted it in the beta group. I was not 100% sure it couldn't be done and that was made more uncertain when Frances's reply to the OP did not say it couldn't and appeared to give instructions as to how to defeat the default message.
It is not that the message is too long; it is for my personal reasons that I find it too terse for inviting people I already know. I wanted to make it friendlier but at the same time not clutter it up with irrelevant wording that I dislike. I will not attempt to justify my reasons as that will simply result in a battle of others trying to knock down my personal preferences as has already been started.
In? future I will not be using the Invite message but will create my own from personal email.
Matter closed for me but maybe not for the OP and at least one other.
Mike Strange