I would look more at the rotation of the cleat than worry about forward and back. SPD-SL pedals tend to self-center and try to push your feet to that position. If that isn't what your feet take on their own, you may be feeling the effects of that force. (I haven't ridden SPD-SLs but I believe they are similar to the old LOOK Delta cleats I've been riding for decades.)

You might try riding a short ride with the bolts to the cleats just barely tight. Twist your foot until everything feels right. Stop at a wall or fence you can grab, not twisting your foot at all. Carefully pull your feet out of the shoes without twisting them. Now tighten the screws. Mark the cleat location on your shoe with a marker or tape. Go ride the shoes again. Better? Keep trying, marking all your changes. Go for longer rides and keep track of how you felt and the cleat positions.

I have knees that are very sensitive to cleat rotation. I document how far the ball of my foot is from the crank and likewise my heel. I have to mount my cleats in different rotations right and left. If I didn't do this I would have had to have my knees replaced or quit riding many years ago.