In free states could there be legal issues carrying a Polymer 80 assuming you have a CCW? From my research, there shouldn't be any requirement to have a serial number engraved just due to it being a carry pistol.

The only one I can think of is if you live in a state that requires that you list the gun manufacturer and serial number for your license.

Residents of OK would have an issue with home built firearms.

I went ahead and had a serial number engraved on mine for a couple reasons. First, in case I do carry it and have to interact with a cop for whatever reason (whether it's a defensive shooting or just a traffic stop). I don't want a cop ignorant of the legality of homemade guns to think the lack of a serial number is reason to arrest me and let me fight it in court. Secondly, if it's ever stolen, the serial number should make it easier to get it back if it's recovered. Without a s er trial number, I'd never see it again.

I used very easy to remember serial numbers based off the markings on my BCA barrels. My compact's serial number is 9X19-19, while my full size's is 9X19-17.

Where or how did you get it engraved?

I took them to a local FFL who specializes in coating, stippling, and engraving guns. They used a laser to put the serial numbers on the plates under the rails.

I'm not aware of any legal issues in "free states". I think most just consider the aftermath of a shooting. What looks better in court, a stock looking "dime a dozen" Glock, or a full custom looking "non serialized" firearm? It may bring up more questions and insinuations than you'd like. If that doesn't cause you any concern, then you should have absolutely no issue carrying the P80.
The other (minor) issue is FAR better holsters are available for stock Glocks. My favorites are Vedder, SL 7ts, T1C, etc. NONE of them make anything for the P80.

I wouldn't use a home-made gun for self defense.  It doesn't do anything better than a serialized version but it opens you up for more questioning, which you really don't need.

Agreed. Lawyers, Judges and Juries are not always reasonable people. They are often quite the opposite. Why bring more issues into an already hostile legal situation of using a handgun in a defense shooting?

Thanks for the input everyone, I think I will continue to use the P80 for carry at least for the near future despite possible issues that could arise.