Something else to look for while at the Depot, is window glazing shims or spacers. They keep the frame spaced away from the glazing at the thin edges, (see how they're usually used in this illustration
by Lamateck) and they'll also keep the frame away from the flat glazing surfaces as the frame is tightened onto the glazing if used on the flat surfaces of the glazing at the edge. Cut them to appropriate size, or maybe wrap them around three sides at the edge of the glazing if they're flat and flexible.
The edge of the frame open to the elements needs a continuous bedding around it, so the spacers should be set back from this edge. With the spacers in place on both sides, inside and outside, of the glazing, tighten all you want (within reason
) and you won't squeeze out all the bedding, which would give a dry joint
but one that leaks
The spacers are very important if you have glass glazing rather than Perspex (avoid Lexan - it clouds) as they allow flexing of the hull without stressing the glazing.
If you direct bolt the glazing onto the hull, oversize the holes in the glazing to avoid stress cracking/breakage of the glazing caused by hull flexing. Countersink the outside (top) of the hole, and pack with butyl tape to seal. (See Maine Sail's excellent write-up.)
Good luck and no leaks!
"You start with an empty cup of experience and a full barrel of luck. The trick is to fill your cup before the barrel runs dry." - bljones