Can we set Referral link as username only?

Affiliates Plugin states:

The plugin automatically generates a referral ID for the user based on their username along with a unique number. It provides a Referral URL including that code for referral purposes.

Is there a possibility to set the affiliate link to ?ref=username (without adding the unique number). My system is already set up for this and I would like to only use this plugin for front end tracking.

Any suggestions?