Does the HS Thorntail work with a PEQ at the 12 o'clock?

If not, the alternatives? I am right handed and run my light on the 9 o'clock.

If you're talking about an Insight ATPIAL, no, not if they're mounted near each other on the rail.

If you mount the "PEQ" farther back, and the Scout further forward, it can work, but you'll have heavy shadowing with the IR illuminator.

The only two mounts I'm aware of that will work at 11 o'clock are the Thorntail Dropwing mount (which only works on a small handful of handguards) and the Unity Tactical Fusion Scout Adapter with one of their Fusion Micro Hubs (this mount pretty much has to be mounted on the 12 o'clock rail).

ETA:  Here are a couple pics of the different ways you can run the Unity Tactical mount as well as the Dropwing.  This is an old setup of mine.

11 o'clock (more like 10 o'clock):


Opposite side with a tape switch:


Dropwing setup:

I do mean the ATPIAL. I might run it 9 o'clock with the factory mount or something similar than. Maybe invest in a tape switch.

Does it shadow really bad when you adjust the ill lower?

Lower, as in using the elevation adjustment?  You'll get heavy shadowing no matter what you do if it's offset on the illuminator side of then gun because of how close the scout is to the illuminator.

If you use the stock mount at 9 o'clock (or pretty much any standard, non offset mount), or if you offset the light to the 7 o'clock position, you won't have the shadowing issues.

I mean lower as in adjusting the illuminator. Not for windage or elevation.

I run my m300 scout in the 1 o'clock position with a thorntail sbr mount.  My atpial-c is on the 12 o'clock rail back just a bit.  My light tapeswitch is mounted at the 11 o'clock position.  The lasers are clear of obstruction and the illuminator is clear.  Just need to find the best place for the atpial tapeswitch, or do the dual switch.