All,

I have posted in the optic section and gotten some really good reccomendations. However, i am hoping maybe someone with a CX4 can share their experiences.

I would like to get a always on or motion activated sight for this gun.

My original thought was a Aimpoint PRO but I am wondering if it is too big?

Wants/needs:
Must be on without pushing buttons or switches.
Will be used behind a light (TLR1/X300) so washout is a concern.

Considerations:
Aimpoint PRO and just leave it on.
Aimpoint H1 and just leave it on...price is a bit high though
Trijicon RMR dual illuminated, concerned about washout with amber reticle.
Trijicon RMR LED, I have read you can leave them on?
Leupold Deltapoint 2
Meprolight Tru Dot, appealing but they are not available yet and $400 is a lot to spend with zero history on it.
Trijicon reflex, again concerned about washout.

Thoughts and other ideas appreciated.

If you want to be able to co-witness with the iron sights, it's going to have to be low.  An AR-height optic is just going to be too tall to use with a normal cheek weld.  

I have a fixed base PA micro dot on my CX4 (MD-FBGII), mounted on a YHM-220 riser that was originally intended for an EOTech.  It also happens to be the perfect height to give me a lower 1/3rd cowitness on the Beretta.  I tried several combinations of optics and risers before settling on that one, and they were all either too tall to cowitness at all, or so short that the iron sights obscured the view through the optic completely.  

Of the choices you listed, I would choose a T1 or H1 and put it on that YHM riser.  I didn't experiment with any MRD's, but I would expect them to be pretty darn low, and the ears on the sides of the rear sight might get in the way.

Aimpoint Comp C3

-Same size as Aimpoint PRO
-Mounted in an Aimpoint non-qd low ring
-Stays on all the time
-Dot is bright even with Surefire light on
-Allows lower 1/3 cowitness
-About $450
-Optic stays well clear of charging handle

I have a trs25 on mine. Co wit's perfectly.

I went with the PRO. I would have rather had the H1 but cost was a factor. PSA is having a sale on the PRO so I jumped on it.

My plan was to see how high it was without the spacer in the mount and I wondered about using a 30mm ring as a mount. Thanks for posting the pic.

I put a Trijicon RX30 on mine. No batteries or switches, trijicon powered so it's always on.

You might also check in to Meprolight.

I put on an older EoTech because they sit low.  It works perfectly for the Cx4.

Do you guys think the PRO with the spacer removed will be too high?

I put a Trijicon RX30 on mine. I like it sitting higher than the factory sights.

I went with the PRO and removed the spacer. It sits higher than the sights but the sights are still usable. Sort of a 1/4 co-witness.

I mounted a Vortex StrikeFire way out front. Leaves room to mount the 2x magnifier if/when I want it. TLR-1s on the left side rail.

I think I would like to get a different mount. I have it positioned pretty far forward so the aimpoint mount knob doesn't interfere with the charging handle.

That non qd low mount posted above is something I'd be interested in. Who makes them?

ETA: I too mounted a tlr-1 on the left side. I liked the thought of it on the extended rail but it was hard to manipulate. I have a bottom rail kit enroute
, going to play around with that and a angled foregrip.

I would also like some optics help with my cx4.  I found that I didn't quite like how things were so crowded when I looked through a bushnell that I borrowed.  I'm currently wanting to get a vortex sparc II with the vortex 3x magnifier.  What kind of risers would I need for both, in order to clear the two 1 inch flaps (i don't know what else to call them) that are to the left and the right of the forward and rear sights? Or is that just plain ridiculous?

I'm new here and to guns. Please don't laugh :)

Most people refer to them as 'ears'. I tried mounting a Bushnell 1-4x32 scope on mine and since the scope was longer than the distance between the 'ears' I could only get it to clear with a long high height rail riser. It worked but was too top heavy & cumbersome and put the scope higher than I liked. Also tried a red dot with a 5x magnifier, wouldn't fit. Only scope I ever found that was small enough to fit was an NC Star 2-6x28 compact I had mounted to another rifle, not the best quality but it held zero and was super cheap. I also had a reflex sight mounted forward and I had enough room to mount the compact scope on a cantilever QD mount behind it and would focus thru the reflex sight when it was off.    

Aimpoint