Having made new sporran chain-straps myself, and refurbished vintage versions, you appear to have made a very nice, neat job of yours - obviously better than the one you replaced.

Vintage chain-straps are found in a variety of qualities and sophisitication of construction - unlike the generic modern version which are invariably simple hide with rivets.

The older ones are often better quality leather with a lining leather and very find edge stitching, and the ends are stitched in place rather than riveted. You can also find the buckles are leather-bound too. But unedged and unlined leathers are also common.

The problem you mention about getting the buckle placed centrally at the rear is something I thought I was the only one it troubled. As you have found, it is easily solved, so good on you..!