The front mats come without the slots cut for the securing hooks in the floor pan to go through. They're easy enough to cut myself but should I take them to an upholstery shop to edge stitch after cutting or is there a DIY trick that will work? 

Also the included firewall snap fasteners don't seem to be the same size as the original or do they need a little more initial force to mate?

Stitching will be the nicest looking I guess but a soldering iron works well too, melts any loose threads.