Hello,

Here is a BIP that matches the reference code that the Segwit2x group has built and published a week ago. 

This BIP and code satisfies the requests of a large part of the Bitcoin community for a moderate increase in the Bitcoin non-witness block space coupled with the activation of Segwit.

You can find the BIP draft in the following link:

Reference source was kindly provided by the Segwit2x group.

Best regards,

 Sergio.