The 350 ft loop is an irregular rectangle in shape. Time permitting I am going to re-lay it out as a square to increase the cross sectional area.
I set up the smaller loop yesterday afternoon, it is roughly a square 12.5 foot on a side. I made it with a 50 ft section of coax, using the shield, hoping the lower inductance of the large diameter shield vs #16 wire will help. By the time I got it done, the higher bands were starting to close already, but some quick tests showed it generally produced stronger signals on 25 meters and up, vs the larger loop, which seems reasonable.