A different approach.
I’m just watching Swamp Loggers and they posted a little note that cypress is a choice wood for items like telephone poles because its resin is a very effective preservative with insect repellent properties. Good for you, cypress
I remember reading a US Forest Service paper which cited southern pine as the best wood to use for posts. Your first impulse might be to ask in what dreamland is southern pine the most rot and pest resistant wood around; the fact is it isn’t by a long shot. What makes southern pine the best choice for posts is that it absorbs any applied preservatives better than other species of wood.
There’s more than one way to skin a cat.