Nice setup! Clean, easy and effective.
Thanks for posting the photos. Will give the other recordings a listen.
Maybe angle the mics inward, pointing them toward the center rear of the stage, but only to the extent that the PA speakers remain fully within the good smooth-response front coverage angle of the pattern. That should help with a touch more drum transient clarity without making the drums significantly louder. And might otherwise beef up the acoustic center a bit.
I thought about angling them from "outside-in" a bit like you suggest. I'll give it a try next time I'm up there. With the low ceilings and a fun-lovin crowd, my goal is to cut out as much crowd as possible. The room sound in this venue adds little bucause of the size and low ceilings. It would include mucho chatter and such. That is also the reason I have started with cards. I may add a center omni to see how that works, but then I need to bring my MixPre-6, with sort of defeats the purpose of the small, compact setup of the F3.
As long as you have easy access to do it, I'd definitely try some inward angling as that may make for a nice refinement without dramatically changing things. Simple enough and may add just enough on-stage direct sound in a way similar to what a center mic would be intended to do.
The center omni is an interesting idea and will be an interesting thing to try, even if you ultimately decide against it (keeping things simple in using the F3 is a perfectly good practical reason to do so). If you find you really like what it does you could leave it up and then have the option to use it or not, depending on who's playing and what you want to carry in.
If you do try it, I'd hang it closer to the stage than the cardioid pair - probably from the same ceiling truss that the PA speakers are hung from which places it directly over the front of the stage, or maybe further in over center stage. Which position is better may depend on the performance. Over center stage will get it a bit farther away from the audience and act more like a drum overhead, while over the front of stage may a better option for things like acoustic instruments up front, solo singer songwriter type stuff. If you like what it does but find it adds too much audience, a cardioid from the truss with the PA on angled pointed down toward the back of stage should reduce audience contribution by ~6dB or so. Only one way to really know.
Either way (angling the cardioid pair, adding a center mic) the intent is reinforcement of the center of the image with increased pickup of on-stage sound - in particular dynamic transients which never really translate through the PA and make it feel like being on stage or right up front.