How to mount a good white light with the ATPIAL has been solved by Unity Tactical and TNVC.
Pictures are of the following setup - LWRC Six8 UCIW with ATPIAL C, Unity Vtac Micro Hub + ATPIAL Adapter (Right side) + Unity flip up front sight + 1" ring, used with a Surefire Fury P2X light and a T1 red dot. Total rifle as shown weighs in at 7 lbs, 13 oz. and 24.5" OAL. I mounted the flip fronts in front of the ATPIAL to get maximum sight radius and declutter the area on the top rail.
Front sight up from two angles
All lasers and illuminators clear the light and irons without backsplash as intended. The IR laser looks close from that angle, but does not actually interfere with the beam as confirmed with my NVGs.
Front sight down from two angles
Again, all lasers and illuminators clear without backsplash or interference - even with the diffuser down on the IR illum.
Top View
Pros
1. Allows use of back up irons, with a great white light while providing slaved vis/ir lasers and onboard IR laser illumination
2. Offers several different configuration modes with front sight in front of or behind the ATPIAL and with the light mounted to either side of the forearm. (Note you will have to buy two different adapters to do front/back and side/side as you wish. If you can narrow down what you are looking for, you can eliminate one side.
Cons
1. Is not compatable with Spikes BAR fore end as the scalloped ribs interfere with the mount. It did work with my rail systems from LMT, Colt, LWRC, etc. May want to verify it works with your rail.
2. Mounting the light on the side can limit access to the fire button on the ATPIAL. If the new TAPS switching system is reliable, this may be your one shop stop. It is certainly reachable but not ideal as is. If the TAPS works as advertised, I'll move the light to the right side of the rifle and run a dual switch on the left side. I just really hate the switches available up to this point.
On the whole I'm very excited by the possibilities. Hope this helps some of yall trying to find white light setups to go with the ATPIAL.
Cliff's notes - buy the RIGHT Side ATPIAL adapter if you want the light on the RIGHT side of the rifle with the hub to the REAR of the ATPIAL OR, if you want the light on the LEFT side of the rifle AND the hub forward of the ATPIAL. Buy the LEFT side ATPIAL adapter if you are looking for the opposite. You won't be disappointed in the quality or integration options on the kit.