Nice Job. Don't worry about the divot taking away from strength you have plenty of sidewall there. I like the thumbwork you've done so far around the mech to smooth things out, the mech pin cover holes are a nice touch, but prevent you from removing the mech so they need to go. I know that Thumbwork sanding around the line release is tedious.. but you should move the ramp back a little so it's easier to get your shooting line back around the line release with a gloved hand. Get a Ruler and measure it out so it's symmetrical on both sides and maybe use a Dremel with round barrel sanding bit to remove some of the material and get a uniform shape and round to the ramp then hit it with the thumbs. Use heavy grit sandpaper for that stuff to start, like 40-60grit and then work your way up or it will take a life. It's great that you didn't seal that gun with Epoxy. First, it doesn't need it, but because it's your gun and build you can easily adjust things and shaping etc and then just brush on some oil. I like the Muzzle shape. Looks like you have room for a third band closest to the muzzle tip which might be nice if this is a 5/16" Shaft, or you could opt to use the third hole furthest from the muzzle as an optional 3rd band. 2 x 16mm small Id this gun would shoot a 5/16" or 3 x 14.5mm. One of the two most critical measurements in Speargun Building is the distance from the top of the band slot to the bottom of the shaft track. Smaller the better. The Band Holes are nice, but unfinished. I know you were worried about strength, but be more aggressive there. Look at a HATCH Rhino for inspiration. If you want that raise to be functional it will need to be deeper. Use a Dremel BArrel Sander Bit and deepen that up a bit. I don't see a Muzzle Line Channel? You won't need the Line Guide as it's Enclosed Track, but a Deep Line Channel is still necessary. Draw it frist with a Ruler and Pencil so it's straight and in the right place. Start the Cut with a Hacksaw Blade to depth and then round it out with a small circular file. Deeper is better. One other thing to consider is a Shooting Line diverter about 10" infront and below the Line Release. This will keep your Shooting Lines down and out of sight and away from your bands. Looks Like a THUMPER, and will be a good Lower Vis WSB Gun. If it were me, I'd rig with 2 x 16mm Small ID at High Stretch or 3 x 14.5mm and if it's a WSB Gun, go with 7.5mm or 5/16" threaded shaft with Mori Slip Tip. The other thing I'd put on that gun is a Reel..