Yes, that looks just right. About two years ago, I restored another Ampeg Devil Bass, where a previous owner had filed out the corners of the triangular cutouts to sharp points. It didn't look good at all. I can't really say why, but the sharp corners didn't look right with the rest of the shape. I filled and recut the corners with wood and epoxy, to bring them back to the 1/8" radius (1/4" diameter), and it looked much better.
The proportions that you've ended up with for your Devil Bass are interesting and nice looking. Smaller, slimmer, more practical. The Ampeg Devil Bass body is really quite large, very wide and quite long. Note how much farther the body extends behind the bridge. Yours is the Devil Goddess Bass.
Have you decided where you are going to put the upper strap button? On the Ampegs, it's on the back of the neck, right up against the body heel. Terrible design. Bad neck dive, strap interferes with your thumb, strap easily pops off the button, etc. On my new Devil Bass, for a while I was thinking of putting the strap button on the tip of the upper horn, and adding an aluminum reinforcement plate inside the horn. But I gave up on that. Too complicated; too many potential problems.
I came up with this extender plate, for use on the original Ampegs that I'm restoring. It's made from 1/8" aluminum plate, and attaches to the back of the body in place of the original neck joint cover plate. The plate has an arm that extends forward about 2", with the strap button on the front face, facing forward. The center of the button is about even with the bass side edge of the neck. This has worked out very well. The balance is fixed, and the button is mostly hidden from view to avoid breaking up the symmetrical look of the cutaways and horns. And it doesn't interfere with your left hand playing up high. Your thumb slides between the neck and the plate. And it's very difficult for the strap to pop off the button. I'm going with a more refined version of this on my new Devil Bass, integrating the curved extension into the recessed neck plate with a recessed brass name plate.
I recommend something similar for yours. Saw it out of 1/8" aluminum plate and round off the edges. Bolt the strap button on with a 6-32 socket head machine screw threading through the plate, and a nylock nut on the back to lock it. Leave it satin finish or polish it up. The one on this Devil Bass, #317, is satin finished. The ones I've made more recently, I've polished up and had nickel plated, to match the original hardware.
Also, another Ampeg tradition is to put two strap buttons on the back end of the body, spaced apart evenly. It keeps with the symmetrical look, and the bass doesn't tip over when you lean it up against something.
