I have installed 5 pt harness in one of my vehicles. I am using the stock seats. (high back buckets). Initially I stripped the frames down, modified the metal framework to allow the seatbelt/shoulder harness to come through in the middle vs hung around the sides. For the cover (stock so far), there happened to be a seam I opened up ~4" wide, and sewed some "lockstitches" on each end after I split the seam to keep it from opening up more. It works good but the seam itself sometimes looks a bit unfinished, especially when I have the 5 pt harnesses removed (don't use them all the time, still have stock belts also).
Any ideas on how to sew up a "slot". Aftermarket seats almost all have big plastic inserts in them which I don't really want.
Not my seats but gives you some idea of whats going on.