English apostrophe rules are not difficult to master. Just remember that all possessives need an apostrophe and an "s" at the end. If the word already has an "s," it only needs an apostrophe. If the word does not already have an "s," it needs the apostrophe followed by "s."
So a name or other singular noun that ends in “s” (like “Chris”) is usually made possessive with the addition of an apostrophe plus a final “s” (as in “Chris's coat”). ... The general rule extends to proper nouns, including names ending in s, x, or z, in both their singular and plural forms.
Is epoxy better then polyurethane?
Epoxy is tricky to work with. If you are skilled with it you can do it but you can easily mess up. Epoxy paints are more rigid, hard, and brittle. So, it will crack if exposed to temperature changes. Polyurethane is more flexible than epoxy because it has plasticizers in the formula. Its plastic nature makes it stretch and contract based on temperature changes. This gives it improved flexibility.
So for outdoor, polyurethane is better than epoxy because it is flexible and can cope with temperature changes. For a more lasting finish, do 5 coats.
Check out these references:
11 Best Clear Cedar Finish for Outdoors ( 2023 Reviews) (woodworkingclarity.com)
or L-brackets
Here is a picture that shows another option on how to mount a sign to a vertical post. Screw a plate to the end of the sign and then screw the plate to the vertical post.