What is the best option for a light on the Scorpion? I am leaning towards a surefire x300u.

I'm struggling with this at the moment.  The way that I hold it, my support hand covers the bottom and both side rails.  The top rail is too far back unless you mount a thorntail behind the front sight.  I wanted to mount either my M952v (overkill, but I have one sitting around) or a TRL-1 (more likely) on a 45 degree mount at 1-2 o'clock, but I'm not sure that the mount will fit on the side rail because of how shallow the rail is; the M952 won't even fit on the rail, because the lever interferes with the handguard.

Surefire scout in a thorntail mount on the left side rail works for me. It projects it far enough forward that I don't have to compromise my grip.

I am in the same boat as you. My grip makes mounting a light didficult.

I use a Surefire Scout with the clicky tail cap on the right side (ejection port side) of the gun. I do this for a couple reasons.

I am a righty so I didn't want anything getting in the way of my left hand and the grip I have with the vfg my palm is resting on the rails on the left side. I am still able to activate the light with my left hand by gripping the vfg and using my thumb on the tail cap. To be honest though I am not a tactical ninja, and the few times I used my light I have needed it to stay on, hence I went with the clicky tail cap that I can leave in the 'on' position or strobe as well with my thumb. Having to change my grip to strobe the light isn't an issue for me because of the lack of door-kicking-in that I do, and the grip to do so isn't uncomfortable at all because of the position of the light. In fact, it is much easier to activate the light with my thumb with the light on the right side (ejection port side) than on the left. With the light on the right side, I can maintain my grip on the vfg, and just swing my thumb around to the other side to activate the light.

I have also had issues in the past using a light on the left side rail. The light would sometimes get caught up on my other gear or on my shirt. It also digs into my body when I sling the gun up on my back when I am walking to change or setup targets and not actively shooting.

ETA here are pics of my grip with the scout light:
"Normal" Grip:


Thumb on the light:

I'm going to try my TRL-1 on the Thorntail 1913 adaptive offset mount.  This will allow me to mount it to the right side rail and position the light at 1-2 o'clock, and also has forward adjustment if need be.  The rail attachment is thin enough that it won't interfere with my grip.

I bet a M300c with tape switch would be tits

What about a x300U-b with a switch?

That looks like a simple and effective setup.  No pressure switches to fail or snag on stuff and easy to use.  That's basically how I set up and use lights up on carbine length AR handguards wit out a switch.  I like it.

Mrgunsngear had an Inforce light on his which looked like a nice fit.

I used a TLR1, mounted at the 6 o'clock position, with a tape switch and it works well for me.