Ok This is Mike's wife, Melissa.. The D-1 through D-4 doublers are shown on page 3 in this thread. (But are not marked as D-1-4) D-1-4 is your lite ply doublers that goes on the inside of the fuse (drawn on the plans but also I knoticed not marked with the D1-4 but is drawn on there , just look at the plans you will find or locate ever piece ) 1 goes front wing adjuster doubler in fuse side , 2 is wing tube doubler in fuse side, 3 is the back wing tube adjuster doubler in fuse side and the D-4 is the stab adjuster in the fuse side ... you will have to cut holes in all pieces for tubes and adjuster holes .

Hope this helps.
Melissa