I would like to get some input form those using a fixed LMT BUIS in front of an Aimpoint.
How do you like it?
Does the BUIS limit your FOV in any way?
Does it co-witness nicely with the red-dot and a standard AR15 front sight?

I currently have an ARMS flip-up BUIS. But I am finding it difficult get low enough on the stock to get a good sight picture so I am thinking about switching to a fixed rear sight.

FYI I currently have my Aimpoint in an ARMS cantilever with spacer.

I'm using an M2 and an LMT BUIS.  It's a good setup.  The ARMS #22M68 with cantilever is a great way to get a decent cowitness.  It'll cowitness in the lower third of the optic.  If the Aimpoint goes for any reason, just drop your chin a little bit and you're using the irons.  The Aimpoint tube will limit your FOV a little bit, but I don't think it's a big deal.  
I personally think the best setup out there is the EoTech mounted directly to the flat-top with an LMT BUIS.  Keep the large aperture up and look through it to get an absolute cowitness.  The BUIS disappears if you're using the EoTech and if it goes for some reason, just close one eye and you're using the irons.  MJD

Anyone else?