I received an email with three image files attached from the initiator of this thread, seeking help in getting them included in the discussion. I was able to open the files and extract from the images they contained some useful views that better illustrate the nature of the cooler and its lid retaining mechanism.
Figure 1 below shows the general shape of the cooler that is the topic of the discussion in this thread.

- Fig. 1. A cooler used on a 250 OUTRAGE and supplied by Boston Whaler. The true shape of the cooler is seen in this view.
- YETI_CoolerShape.jpg (36.05 KiB) Viewed 2644 times
The initial description of the cooler shape was as a "wedge" which suggested a three-side object. The cooler shape has four sides and is more accurately described as an isosceles trapezoid or a trapezium.
Also seen in Figure 1 are the mounting fasteners for the missing latch straps, which are located just inboard of the hold-downs for the cushion.
ASIDE: The email attachments totaled about 16-Megabytes, which not too long ago would have been considered a "mail Bomb". Fortunately, my email host permitted the huge email to be received.
A note about what it took to get these files to be included:
--the original image included additional portions of the boat that were not particularly necessary to see the cooler's shape. The original image was badly exposed and some exposure compensation has been applied to the image seen above. The original format of the image file was .PNG, which when used for photographic images results in very poor compression characteristics and very large file sizes.
--the original file size of the image was 4,700,000-bytes (4.7-Megabytes); the image above has a file size of 37,000-bytes (37-kilobytes). Although the cooler is longer than its height, the original image was composed in portrait format, and the dimensions of the image were 1620 x 2160. The original image was cropped to show just the cooler and then scaled down to be only 800 x 750.
The reason the OP could not upload this image for hosting by the forum was the file size was too large and the image size was too large.