Add an Exisitng Site from WPMU to WHMCS Provisioning

I am looking to do the same thing as here, except, the only way to disable the module in the product edit screen is to select none, which actually removes the provisioning fields all together under the client's product editing screen.

How else is it possible to link a new client's product site with an existing WPMU site?
Is the DB the next thing I should look at?
I only noticed I can update the fields directly, or add a new row to the mod_whmcs_multisite table
But simply adding a new row (with the correct blog and service id) did not link the information to the client's product. Any other tables to update or check? any other advice?

Thank you.