Where is my mistake? And how to correct it? I have to cut overply somewhere.. should I cut station E or sole?
I didn't answer how to fix the problem. Since the width of the sole in the frames is narrower than the width of the sole, I would draw a sole line on the frame so it extended the true width of the sole. The line will probably extend a little farther than you actually cut. From these points I would draw a parrallel line to the seat sides up to the top of the frame and also redraw the seat edge line. So this will give you your new cut lines, but before cutting I would make sure that the width for the sole is correct and the distance for the seat sides are correct and the same for the seat edge and top.
You should be fine because your sole width was less than the actual width needed for the sole.
Warning this may not be the case for the AR15.
Note: the actual cut out in the frames for the sole is usually 1/4" wider in total than the sole width. This gives you 1/8" clearance on each side of the sole for it to drop nicely in place.
Tip:
When drawing out any piece it is wise to check your dimensions against other pieces that will connect at that point to insure that you haven't made a mistake while drawing out the part. Measure/Check 3 times, Cut Once.
Beer is living proof that God loves us and wants us to be happy.
-- Benjamin Franklin