Hey nrk
Yes I did manage to solve this issue. I would love to say I figured this out on my own but I actually had some coaching from another leather crafter. What he taught me as to make the piece you are doing your tooling on about an 1/8" larger on each side. After you glue the interior and sew it ( I use a machine, no hand sewing for me :-) ) I sand down the edges and it will fill in the gap. Then slick your edges and finish them to your liking.
I hope this helps. Feel free to ask any more questions I will try to answer the best I can