I put my thru-holes much nearer to the tip of the bow/stern, as I didn't want too-long dangly loops/handles being able to reach the water and drag, yet I still wanted room for them to pass over the end of the kayak.  So, about 2 inches back from the tip, and 1 inch down from the deck for me, and I'm quite sure the location is way more than strong enough to pick up the whole kayak (or probably 3) from just one loop.

Lesson learned:  I did my first end pour on a 95+ degree day.  I expected it to get hot, but the epoxy reaction in the big lump end pour generated so much heat that I got a few little "speck-bubbles" in the fiberglass. As they say elsewhere on the forum, they are now a "feature" on my boat.  Kind of pretty as they catch the sun... I put the other end in a bucket of water before I did the pour!

   Mine are 3" (stern) and 4" (bow) and seem fine. I'd recommend about 3" for yours.

mine are about 4 inches back (stem and stern).

fwiw....i do the end-pours and drill the thru-holes prior to attaching the deck....allows for a lot more control of the endpour size and confirmation that everything is as you want it.

h

   Thanks for the info, I drilled them at 3". Looks fine to me, I'll report back if my bow/stern break off!