SO looking at some videos and pictures I noticed how folks are mounting their FF3's on the slide. Some are mounting it flush with NO plate, just using the mounting screws . Others are using the FN mounting plate between the slide and FF3.

Does this truly make a difference? I would think that without the plate the optic can shift slightly and would sacrifice accuracy a little bit. When I put the plate the 2 posts on the plates seem to lock in nice and tight limiting movement. I have not yet mounted mine up, just mocked it up to see the difference.

Which way have you guys mounted up your FF3, Plate or no plate or have you tried both to check accuracy?

...with the plate.  For the reason you describe, is how I mounted mine up.

Mine  is mounted with the plate. Those lugs take a lot of the shearing forces off the screws. I also read that mounting without the plate will result in the light sensor being blocked, thus disabling the auto-adjust feature. No personal experience on that, just what I read.

Also of note, I had to source some longer screws from Grainger (5-20 thread, I believe, but double check that). The ones supplied only engaged a few threads when using the plate.

I got some screws coming to mount my ff3 with the plate. I ordered 10 for me and my buddy's gun. 

send me a pm and if they fit I'll ship you a few to use with your ff3

Received my screws and got the ff3 mounted up with the plate.

#5-40 x 1/2 screws are good for the ff3 and vortex venom.

bought a 10 pack on eBay for 4 and some change shipped.