dw, you still with us?
"I just don't know how strong the stock glass (safety glass with a laminate in it like a car safety glass) really is. Any ideas on this?? Thanks!"
Couple of years ago I was helping to replace a set of portlights with new exact replacements from Mark Plastics. My friend was baffled at how to get the old ones out, because the glazing sits in 1" wide plastic channel that in turn is heavily siliconed into the inch thick cabin side and whatever wasn't leaking didn't want to budge. I said "Let's just knock 'em out and implode the frames" and he said no, that's Lexan, you can't just knock it out.
I took the standard 16" ball peen hammer, ball side out, and went "tink" just from my elbox, backhand. The acrylic, very much not Lexan, portlight blew right out and we proceeded to blow them all out and implode the frames.
How strong are your portlights? Well...If you have a spinnaker or whisker pole "up there" somewhere and it decides to come visit the portlight under storm conditions one day....Doe anything less than 1/4" polycarbonate still seem reasonable to you?
When in doubt, go to a glazier, get a scrap of what you've got, put it in a vice and go "tink" with a ball peen hammer. If it survives, go "WHACK!" with the same hammer. When you get one that survives, that's the minimum glazing to look at.
Unless you're just daysailing with "ceiling and vision unlimited" type days.