Aluminum cooler rack and fishing rod rack help

I just picked up some 8"X8" 1/2" wall tubing. that should be strong enough

Seriously, copy one that you've seen. You're going to get all kinds of answers with such a vague request.

Karl

I think a more reasonable approach would be to fabricate a properly designed assembly with steel, and apply appropriate corrosion protection, or get a vehicle that has room for a cooler and rods.

If you want an aluminum item, you could buy it from a company with deep pockets, so you can sue them when the product fails (driving down a highway, there will likely be collateral damage). If you're unable to locate a product to buy that's made of aluminum, the likely failures from fatigue and liability have probably already been considered.

Unless you're a mechanical engineer and a certified welder, building an inappropriately designed item of this type, could potentially create a lot of damage if it fails.

Why reinvent the wheel? You can buy one for less money than the aluminum will cost you, AND it won't be your butt on the line if it fails.

Mine is a steel unit that works fine. One thing I did do was add a pair of braces on the corners to the bumper. Made a BIG difference in keeping the thing stable.