I marked the fit for both planks, traced the lands from beneath, taped off the plank to reduce squeeze-out mess, and cut the attachment gains to match the receiving gains on the garboard.
I confess confusion about how these matching gains should best be cut. Both books I have are vague about it. I cut 9 inch gains on the garboard strake, cutting down through two of the three plies (the face veneer is thinner than the midline veneer... about 25% of the total thickness for each face, 50% for the inside one.). The slope of the ramp is linear for the length of the gain.
The corresponding (attachement) gain for the next plank is cut on the inboard side of the plank where it mates with the existing plank. But how long and how deep to cut it? I'm just guessing.
The objective is for the overlapping planks to be flush at the stem and gradually reach full overlap at the end of the gain. Given that the existing (receiving) gain is 25% thickness (only the inner face veneer remains), the attachment gain for the current plank only needs to be cut as deep as the inner face veneer (75% thickness).
My strategy was to cut that attachment gain for 5 inches, rather than try for a linear slope of 1 mm over a 9 inch distance. We shall see.
The garboard glue-up required three two-stroke aliquot (two pumps of resin and hardener for each aliquot). The first mix was epoxy only, for wetting out the gluing surfaces. Two more two-pump aliquots were necessary for thickened putty epoxy (wood flour and microfibers mixed in), one for each plank. Today I used a two-stroke aliquot for wetting out, and one three-stroke aliquot for epoxy putty. I added about two tablespoons of wood flour and two tablespoons of microfibers to the three-stroke mix for the thickened putty. Seemed about right.