So I've also been wondering about a front sling mount solution. I tried having a sling mounted to the bottom and didn't like the way the rifle hung. I've been thinking about drilling a hole in the front left panel which would correspond with the extra hole in the chassis and then try to rig something up that way. It appears as though there would be ample room for a small backer on the inside of the barrel channel. The pictures aren't great but they should get my point across. I'm not exactly sure where I would go from there but to me, it seems like a good place to start.