Flexing in middle of 3/4" walnut table top

I am building a table made out of 3/4" walnut. Right now, I have it on saw horses but will soon be attaching legs via cleats. The problem I am having now is that I’m noticing a bit of flex in the center of the table while it’s on the sawhorses. I understand this is due to no supports like aprons. I want to avoid aprons, I am 6’8" tall and I hate hitting them. I have formulated three plans and would like to get advice on which one I should use.

the plans:

1. weld together a rectangle made of 2"x2" steel/aluminum square pip which would be the width of the cleats and the length of between the cleats. Plus I would probably weld another piece of the tube down the center of the rectangle. I would attach this by using some form of bracket.

2. use a product like these metal stiffeners in between the cleats. I’m thinking 3 or 5.

3. ripping some walnut to fit very snugly between the cleats and secure them to the table with glue.

Please let me know if any of these would work and which one you think would be better. Also, if I am overlooking anything please let me know. THank you!