There is no slider for fumbles. Do not set your defensive adjustments to strip balls.
My Heisman Coaching slider set has tackling at 5 and practically everything else at zero and they still fumble, albeit once maybe twice per game.
I can tell you that it takes an entire set of sliders to make the game play realistically, not just one slider tweak. Pass Rush and Pass Block, Run Block and Run Defense, QB Accuracy, Wide Receiver Catch and Interceptions ... they all work together.
I provided you with all the information you need to make your own. Try Oraeon1224's sliders, they are remarkably close to default, which you claim to be looking for.. and there are no complaints of excessive fumbles.