That's plenty wide. If you had stones you could use a 60* stone to narrow the seat up from the bottom. Then take a 30* stone and top cut it. Then take your 45* stone and cut the seat. I ,Ike .040-.060 wide and on the outside edge of the valve face.
My concern is it's too wide. Which it is. LOL. But what problems could this cause other than lack of flow due to the wide single angle. Drivability wise I think will be OK