Anyone use these? I just picked up a slickster, and I'm gonna toss one of these on it. Does anyone make a kydex mag pouch that can go in there instead of the elastic ones? I'm not a fan of the velcro, and would prefer the kydex.

Bumping for info....I'm looking at them too, and am curious about mag retention and compatibility with 5.45 or 7.62 AK mags.  If I knew it would work, I'd put Esstac kydex pouches in them but I don't know that it would or wouldn't work.

I tried the ferro kydex pouch insert. If fit fine but was very heavy on retention of the mag's. I returned it and just used the elastic insert from Spiritus. My main reason for wanting the kydex was for one handed reinsertion of mags. However, the way the chest rig is designed allows for one handed reinsertion using the elastic insers as well. It's really well designed and I've been pleased with it. Fwiw, any mag insert that is compatible with plate carrier kangaroo pouches will work with the Spiritus.

Awesome, thanks. I might try the PIG 3 mag carrier inside of it. Seems like a solid solution.

I bought a RG Ferro Concepts Slickster in Nov.  I also got the Spiritus Micro Chest Rig MK 2.  I haven’t used it yet with holidays & work.  The elastic pistol/rifle inserts are nice and have retention like BFG Ten-Speed Pouches.  It’s thin / low profile. I’ve owned an HSGI micro chest rig and SOE micro rig both which I liked, but I like the Spiritus much more!  It appears well made but I have no idea how it will hold up.

The RG on the Ferro and Spiritus match well if that is a concern.
The Slickster uses CB hardware and the Spiritus uses black.

I like the Spiritus "SACK" better that the Ferro "Dangler".  The "SACK" feels thicker, better made and has a nicer zipper.  The "SACK" doesn't have Velcro on the front like the “Dangler" if that matters.

I’m 6’3’ and 200lbs and the "Micro Fight Fat Straps" kept trying to slide to the edge of my shoulders.  Something like a "PIG Sternum Strap" might have worked which I didn't have at the time. When I returned the straps Spiritus suggested trying the "Skinny Strap" which might work as it crosses in the back.  I may also try the "Haley Strategic D3CRX Harness" (which is out of stock) as the attachments appear to be the same. Haley isn’t planning on making RG but CB would be fine.  For now I'll leave it on the Slickster which I plan to do most of the time anyway.  Shoulder straps are just in case I decide to use them.  

I don't care for items on my thighs unless I'm planning on being stationary.  I tried the HSGI leg rig sometime in the past.   When cinched high it was ok.  That said I seen a photo while researching the Spiritus MK2, where someone attached extra straps and it worked like the HSGI leg rig.  Pretty handy.

There are not many reviews on the Spiritus MK2 or the Ferro Slickster.  Here are two I recently ran across.  I hope this helps.  Personally I like both.  It's like they were made for each other!
Spiritus MK2 -  https://youtu.be/Ee35R47TRw4
Ferro Slickster - https://youtu.be/HdmTGd8TXUA