I carry a Zev OZ9 compact W/ Surefire X300 and RMR IWB appendix but am looking for a OWB holster that I can use when I need to tuck in my shirt and wear a suit jacket. I'd prefer something open ended or longer so I can run as a 'Rowland Special' or one of the longer (17/34) length slides. Any recommendations?

Most concealable/comfy OWB I've tried.

https://gunfightersinc.com/product-category/ronin-owb-holster/

@3one5  Have you looked at just getting tuckable loops for your existing holster?  In stead of getting a whole new holster it’d probably be cheaper.

I have a belt slide holster from International Handgun Leather for every pistol that I own.
IHL, check em out.

Bianchi model 75.

You will get many different suggestions, it’s kind of like asking about shoes. My personal favorite OWB kydex holsters are from KT Mech or Concealment Solutions.

The gunfighter ronin is comfy, BUT not even close to being great for concealment. It's barely OK. I have one for an M&P compact. I liked it and use it for training. way to bulky of a holster for concealment. Purchased one for my 1911 to use for training. Could not send it back fast enough. Quality was horrible!! They seem to be going downhill.

Leather or Kydex?

Straight up or canted?

Drop in or retention?

Belt loop or clip?

I like a thumb break for OWB and I have a very well-broken-in Mitch Rosen Express for my Kahr 45.  It conceals well and gives something resembling "retention."    It's how I carry my Kahr .45.

I have a High Noon Holsters "Hooker" (no joke, that is the name) Kydex for my J-frames.  I really, really like it.  High Noon has a ton of OWB offerings and crazy names for all!

I am in the process of getting  a 2A Holster "Liberator" for my J-frames.  This will clip to the belt and should be easier to get on compared to the High Noon Holsters "Hooker."  

For open carry I like Safariland ALS (Active Locking System) paddle for my 1911 but my mid-section is too short / too much of a "high ride" to draw efficiently.  I have to literally bend over to my left to clear the holster on a draw.  

Andrews Leather is a great, great company and man to deal with, give him a try.  He does some really nice work, and in like 20 different exotic leather skins if you want to go that route.

Good luck, let us know what you get.