I’m considering making the jump to a red dot on my 19.5 and have a few questions.  I’ve read threads here about the preferred vendors for milling slides and have looked into that, and it seems that after a refinish and maybe adding some front serrations the price is getting pretty close to what you can buy an aftermarket “Gucci” slide for.  Particularly I stumbled across the Zev Citadel slide for the 19.5.

On the Zev Citadel, will it fit my existing G-Code holsters for the OEM 19.5 or are they profiled different enough to make a difference there?  Also, would any reliability issues potentially come up with the aftermarket slide?  Last, I notice in the description for the Zev slide it says it comes with a RMR adapter plate which I am interpreting to mean that these are somewhat like a MOS slide and not cut specifically for an RMR- is this accurate?

The main reason I am considering it is due to the downtime of sending my slide off for milling and refinishing, and figured buying the Zev would be a wash (or slightly cheaper) than having similar work done to my factory Glock slide.  However, I don’t want any potential for reliability issues and also have read enough to know that a slide cut specifically for a RMR seems to be preferred over MOS-style adapter plates.  

Sorry for all the questions but hoping for some guidance here on a subject that, despite being a lifelong gun enthusiast, I am not very familiar with.  This is new territory for me.

Having had a G21 slide milled and wishing I could switch back, buy a slide or sell the gun and get an MOS model.

I milled my duty gun (issued by the city, not mine) and my off duty gun.  Works great.  We don't issue MOS guns (If I had known we were going to issue RMRs I would've switched us to 9mm MOS guns)

It's your choice.  Don't expect to regain your money if you sell it.

I did one of each... a Swenson ready milled slide for a Vortex Venom (around $220) from Midway USA, to which I just swapped the parts form the donor G17.3, and a G17.3 that BattleWerx milled for the Trijicon RMR...I just added some cold blue to the machined surface and some Birchwood Casey Barricade protectant before bolting down the RMR... will see what it looks like in October when I change the batteries...IIRC BattleWerx was around a 10 day turn around and they contacted me every step via e-mail...the Swenson slide had an oxide like coating... neither gun is outside in the elements and not abused... the RMR is a dedicated house gun, and the Venom is a carry optic competition pistol for USPSA and Steel Challenge

the pre machined slide was a trial to see if I wanted to spend money for the higher priced Trijicon... and not really about which machine work I would choose