Nice add-on for Sliced Invoices

I was looking for a plugin which can create an invoice from contact from 7 submission and this plugin do what is talking about and is quite simple for set-up. Unfortunately is not in 100% accordance with legislation in Slovakia and there is no many ways how to fix it. I am missing some fields, which i can with few javascript add to the extra field, but also missing delivery date (created date and due date is not enough by us, we need also delivery date because of tax) and other many little things.

Also there is i think a bug, if is invoice created form contact form 7 submission, the due date is not automatically set in invoice and need to be edit manually. If i create invoice manually in WP admin, then the due date is set.

Also i have a question, where exactly i can edit the template for invoice that i can add the delivery date and few other legislation things to the invoice?

Thanks ??