I spent most of Tuesday morning (a wonderful day off) trying to figure out how to measure for the latch openings in the hatch lids. The distance from the lid edge and the inside of each notch and aluminum plate measure just slightly different, depending on the width of the top of the frame collar and angle of the frame to the bulkhead. These are "money cut" as I get one chance to get it right, otherwise it's build a new lid.
This is the template I used, cutting out a hole for the Southco latch to use to measure each spot. You can see the measurement for each latch cut, either plus or minus from flush with the edge of the lid.
Later I used this same template for final routing of each lid opening.
Deciding to give my router a break, since I only had a 1/4" pattern bit, I pre-drilled out much of the material with a Forstner bit on my drill press.
Then finished each cut with the small laminate router. Next time (those words keep reappearing), I'll buy a 1/2" pattern bit and use my bigger Bosch router.
Test run of two of the Southco latches. Looking good!