1/2 splits look good. If you want to insure success against bug damage and checking I would still split them into 1/4's, remove the bark and seal the back with 2 coats of pva. 6-7" is a really good diameter for bows, by splitting into quarters you will actually remove stress, yet the quarters will be still be meaty enough to resist twisting when drying. The only drying stresses you would now get is backset, which is a desirable quality in a bowstave. I have only had ever had trouble with twisting on really small dia 2-3" sapling staves, that got split into halves.
You don't have to take them to one growth ring yet, just get rid of the bark as they can hide bugs, buy the time the staves are seasoned you can get disappointed when you remove the bark to find holes into the heartwood.
Once you get them to this stage they will dry quicker and you can decide on a good ring, and learn how to follow one ring, at your leisure. You can work on a unseasoned stave, as long as you reseal the back if you working on a growth ring.
They are good staves.
Hamish