I shoot 3 under and it seems to work out better for me.Some pro's say it stress the bottom limb more then the top though.
Maybe a bit, but in 9 years of shooting 3 under, I've never had a bow issue develope that was related to how I shoot. And I shoot a lot of arrows in a weeks time.
You can reduce the gap at closer distancesby shooting 3 fingers under the nock
yep, it'll reduce the gap compared to shooting split. Where you decide to anchor on your face will also effect the size of the gap at any given range.