The overall quality is great. The only issue I'm having is that when the mag is empty the slide only locks back on the mecgar style mag that came with the gun. Tried a few USGI style mags from sarco and they feed fine but the slide doesn't lock back. I have replaced the slide stop, and while the slide does now lock back on the empty USGI style when not firing. When I shot with the USGI it was the same issue. I'm not sure if I should replace the slide stop again or get other USGI style mags to try.

I'm 99% sure it's the mags. I did several builds over the summer using sarco parts kits that came with their 7rnd GI style magazines. Every one of them allowed the follower to jump the slide stop. I was like you at first and thought I needed to fit a new slide stop. Every build functioned fine with any other brand name mag.
If you want usgi style look for Springfield mags at Brownells. Otherwise I have good luck with chip McCormick.

Don't go modifying your gun to get it to function with Chinese garbage mags!

^^^This^^^

Sarco's mags are trash.  They sell their house brand mags, and also their house brand mags with USGI style markings, but they're both the same thing.  I picked up one of their standard mags a few years ago, and while it fits and feeds fine, the follower would get jammed on top of the slide release.  I worked it over a little bit, bending the tab on the follower and it seems to work 'ok' now, but I'd still consider it a subpar and suspect magazine for range use when I feel like farting with something that probably won't function.  I don't trust it, and I wouldn't buy any more from them.

True USGI surplus mags, other mystery Ebay knock offs, and a factory ACT-MAG all function find in my El Cheapo 1911.  Considering all the other mags out there, I can't see buying Sarco garbage.  7rd GI style Colt mags aren't that expensive.

Buy a single, Mccormick or Wilson mag and test your gun with it.  If it works, sell the rest of your mags and stock up on Wilson/Mccormick mags.  If it does not work, sell the gun.

If you just bought the sarco mags and you bought quite a few, as soon as you confirm the gun works with other mags, you should try to return them to sarco and tell them what they are doing.
As the poster above said, you can bend that lower foot on the follower out a little so it engaged the slide stop. I was surprised that they all actually fed without jamming except for not engaging the slide stop.

Thanks for the replies, I'll try some different GI style mags like the Springfields and see if that works.

As a previous poster said try a Chip McCormick mag. They are what I use in my ATI Commander. Here's a good read on 1911 mags.

http://www.10-8performance.com/1911-magazines/