I just picked up a Streamlight Protac rail 1 and I need a keymod mount for it. I will be running it on a 13'' KMR or a 9'' KMR and would like to be in the 45 degree position and possibly slightly forward. Should I go BCM? IWC?

I'm running a Arisaka Offset Keymod mount for my RM1 light on my 10" AR Pistol.  GREAT Mount!

Check it out here

For a rail like the kmr that has mounting spots at 11 and 1 o'clock I like the inline mounts like the haley or arisaka.

Yea I am leaning towards the inline mounts for sure. Still not sure if I want to run the regular end cap or if I want to run the pressure switch.

Super happy with my kac

I have been extremely happy with my Arisaka Inline Mounts. Their newest generation almost makes me want to update mine-- the 7075 version is slimmer, lights, uses the BCM nuts, and is cheaper than the alternatives. The BCM nut thing put my mind at ease, as I have seen some horror stories with keymod accessories messing up rails...makes me feel better when I put Arisaka stuff on my $200 rail that I know they are using OEM nuts that are designed to work with the KMR.

This is the one that I'm eyeing to update to:
http://arisakadefense.com/products/inline-scout-mount-keymod

I have a half dozen keymod scout mounts. Arisaka forward catilever mount will cause light to interfere with MBUS bolt or arm at the upper 45 angle mount position. The Haley IWC mount is heavy and not high or tight enough, very wide left only slightly up. The MI is cheap plastic. The V7 is just OK but better position than IWC (which is my least faborite). Love Noveske for how high and tight it is but it would be too close for anything bigger than a Scout and too close for certain lasers. The adjustable Arisaka is the best option. I have a non forward cantilever that is my 2nd favorite with MBUS but cantilever is 2nd favorite with non MBUS.

Is this the one you're talking about? Will that one clear an MBUS?

This one will clear if you use the low or middle mounting holes.  If you use the high (Top) mounting holes, it will interfere.  (I have this mount and love it)

Exactly correct

BCM offset scout mount, Magpul MBUS Gen2, Surefire M300 Scout:

Pushing down on lever:


Not pushing lever:


Side Clearance: