Help determining square steel tubing size for a gate

I used a 5" diameter schedule 40 Galvanized post with caps available 4 plus feet in the hole, 12" scrap welded to post in a few places at 90°, 36" diameter hole and as much concrete as needed.
1 1/2" tubing horizontal, 2" vertical, redwood 2 x 4 's attached to the 1 1/2" tubing with galvanized 1/4" bolts. Dog-eared 8" redwood with all wood sanded and multiple coats of quality deck stain. Used stainless screws for fence board attachment level and 3/4" from sides.
A 2x4 for a stop with a sliding quality latch was securely screwed to the house with lags.

This was about 15 years ago. Sold the house in 2011 and house had sold again a year or so ago going through an addiction and major remodel, gate untouched.

BTW the gate a bit taller than 4 feet. Been through a lot of properties as a Surveyor over 40 years and cheap wooden or even wrought iron fences and gates are not the place to save money.