I also plan in building a canopy of some sort for the top. The only improvement I would recommend is to point out where the bolts to secure the top rail should go. You might have said and I probably just missed it. That and I used cedar 4x4s and they measure 3 3/4 where I think your plans went off a 3 1/2 wide 4×4. I’m gonna wrap a 3 inch tall peice of copper around the bottom to protect when mowing and such.