I'm heading some of the same direction you are on my x39.
Have a 6" and 2" section of rail coming, a Magpul AFG2 will go on, and for the time being I'll have the option to hot swap my Surefire X200 from my 1911 to my AK till I get a Streamlight or similar with some decent output and range.
I agree on the stippling, either the whole thing or none. And personally I would've done it with a smaller appliance so it's more sandpaper and less pebbly in texture. That said, I agree on outfitting the factory handguard. It's a good, lightweight piece. I just needs some work to suit to the user's needs. I'm definitely stealing your idea and moving my buttplate sling point to the handguard since I have a single point sling adapter on now, and my sling can swap between single and dual point if I have a sling attach point on the foreend.
Good job on the cutouts! Good advice going on here.
With my next attempt I will indeed use a smaller solder tip to achieve a more uniform and sandpaper like texture. To be honest this is the first time I have stippled anything, and all I had was an old worn out tip that I didn't mind getting plastic all over. Good learning experience either way.
In the picture I don't have my flashlight mounted, but it is usually sporting a streamlight polytac in 1" rings on the forward rail. I thought about swapping one of the direct mount M lok scout mounts for my light to save some weight. Bolt it right where the rail section was and eliminate the rail and separate ring setup.
I really like having that sling attachment there and it's about as light as it gets! I actually added another one to the buttstock where it meets the receiver for my single point. Works great!