Ok...so with the help of MojoAxe, I got a pair of their small head #8 screws, which I used to affix the Dunlop Straplocks to the Doubleneck.
I went in around one full inch, for added, security and was carful to avoid the truss rod. With these larger, thicker than stock Gibson necks, that wasn't a problem at all. I used a full 45° countersink to protect the black polyurethane.
At a full 10-1/2 pounds, I decided to make a custom strap. I found the Double neck to be more comfortable when worn up high, about where you see Don wearing his here:
Don actually wears it a little lower these days:
Note the 3 hole truss rod covers - standard production on the Don Felder signature EDS-1275.
I found that the most comfortable position for the Double neck is to approximate the same position as it is while playing seated. It is an extremely comfortable guitar to play seated!!! After verifying a good, comfortable position with a common adjustable strap, I arrived at a length/width that I think will work out nicely.
So, I ordered up a double back (finished on both sides) 10 ounce section of leather, about .170" thickness, a full 3" wide with holes on 45" centers and an overall length of 47" total.
Thinking that should do it...