Nice job and thanks for posting the follow-up results! As a suggestion, you might want to look into blowing heat into the leather to shrink them to fit the seats. I've read somewhere that this is how OE and professionally installed leather seats are done, to get rid for the wrinkles.
[edit: here's a diy YouTube video I found on the topic from a quick search]:
https://www.youtube.com/watch?v=aw5s__GfRhg
If taking a heat gun to your leather is a little too scary, I'll bet an experienced pro upholstery worker could do it pretty easily, since you've basically done all the heavy lifting of actually replacing the cover, it appears you only have the finishing touches remaining.
Hope this helps, and best of luck!