if it were me( just cos i am biased towards them!!) i would keep the handle off, as it sounds there is no going back now- and make it a bow that bends thru the handle- it would help the oak a lot too, as the stress would be spread over a greater area.
remember now- that the handle is a lot narrower, so it doesn't need to be thinned much to get it bending a little bit, look at other pics and posts of bend thru the handle bows.
you dont want your handle area bending much at all- more of an elliptical tiller, not a pure circular type shape.
pm roy and ask the ol'fella nicely to show you how to do the computerised circle overlay thingie, it will help you heaps.
if you take too much off the handle- the bow will take a lot of set in the handle area- the area is narrower, reduced surface area, and excessive compression and tension stresses, in this area will induce lots of set! dunno how i know that!!???