Normally, drilling holes in your cooler isn't a great idea, but I did the math, and decided this would work.
I compared the thermal conductivity of stainless steel to both spendy fiberglass/resin eyebolts and tough to find, but inexpensive nylon.
Nylon won, 20% lower thermal conductivity than epoxy resin, and only 1/500th of stainless steel - so decided I could do this without a terrible heat sink to fry my cooler contents.
1/4-20 nylon eyebolt, 2" shank, and 1" seal washers - pumped my drilled hole with the good 3M white marine sealant.
finished the inside with another seal washer, bellville lock washer and polycarbonate nut - cropped the nylon thread foot with a jeweler's saw.
Over-tightening is a bad idea, because it deforms the ABS and compresses the cooler insulation, and the main reason I used the good sealant through the drilled block-insulation thickness.
BTW, began drilling from this side with a small bit until I could increase it to a 2+inch-long bit that would break outside, then finished the 1/4" pilot hole from the outside - the point, the ABS was really tough to get that first drill bite.
Works just like I planned
Since I was buying parts, put an alternate eyebolt in my sternwell slidetrax, using a harmony nut and washer stack (flat plus split lock-washer) to get the clearance I needed with 1/4-20 x 9/16 thread length.
Not sure what it is, but stainless shouldered eyebolts look like jewelry.
When rigging my Kestrel last year, replaced four accessible M5's with them.