thinning pines for blueberry planting

I have about one and a quarter acres of native shortleaf and loblolly pines that are anywhere from 8 inches to 14 inches in diameter and fairly thickly established. I would like to thin them and interplant blueberries and strawberries to establish a guild. My concern/question is how much I should thin the pines to allow adequate sunlight penetration for the development of fruit by the berries. These pine species mature with about a 30 foot diameter canopy and may grow to be 90 - 100 feet tall. I am considering also growing an understory of red Mulberries but am concerned that they will cast too much aditional shade and hurt fruit production.

For now I would only thin enough to allow a fair amount of sunlight, they don't require all day sun, but at least half the day would be good. If you only clear what is needed you can always clear more later, but if you clear too much the pines will take a while to grow back. Also consider huckle berries which are a close relative to blue berries but require less sunlight to be happy. Keep in mind the pines are great at fixing the soil to the correct ph for blueberries