I went ahead with using an internal strap and buckle method outlined in the box pleated supplement. Stitched the button hole closed. Modified the front apron to get symmetry and centering of tartan.

I am currently awaiting the arrival of a piece of tartan fabric to make the new buckle straps to finish up the job...

Then on to altering the next kilt

Any thoughts on two buckles versus three? I have kilts with both configurations... any advantages between the configurations?
My current waist size is 42.5 inches.

Thanks again for advice.