Suggestion Needed

Thank you everyone for supporting me and using my plugin. Special thanks to those who are taking a bit time to write a review of my plugins.

When i wrote this plugin i was not well familiar about wordpress custom post type (CPT) which is a nice feature of wordpress. This plugin creates two database tables to store messages and its meta. But if we use CPT we can get everything need in this plugin and most of the things without reinventing the wheel.
But now in multisite we can access same messages from every subsite, if we use CPT i do not want to make this features. (very expensive in query).

Please advice me should i move to CPT or should not?.

https://ww.wp.xz.cn/plugins/front-end-pm/