Is K9AY loop shape important?

Al Merriman: I would advise you to avoid like the plague the flattened, rectangular K9AYs that some have installed. If you try these I suspect you will be very disappointed with the results.

Guy Atkins: If a defining characteristic of a K9AY is its use of crossed-X delta loops, then I would agree with Al's comments. Maybe the rectangular, fence-mounted loops I use at home is closer to Wellbrook's ALA 100 antenna. This is a broadbanded, rectangular loop mounted in the vertical plane. (On DXpeditions I use the K9AY electronics with normal crossed-X delta loops and a fiberglas central mast.)
In my home installation, I employ the K9AY control box to switch between the E-W and N-S loops and to vary their termination resistance. Directivity results on mediumwave has ranged from nominal to amazing.
Whatever you call it -- flattened K9AY, broadband loop, or a fluke -- this antenna works excellently.

As Walt Salmaniw mentioned in the HCDX newsletter recently, I indeed found performance of the rectangular loops to clearly outperform my best-ever T2FD. (The T2FD was the 7th or 8th I've built for 90 meters, and it had a high quality commercial balun, double-shielded Belden coax, etc.) I compared the antennas for three weeks, and always found signal readability and s/n ratio better on the rectangular loops. Since the K9AY control box is involved it takes some knob-twiddling for optimum reception. The consistent superiority of the loops gave me no reason to continue using the visually-obtrusive 100 ft. long T2FD.

The other antenna I use is a 175-ft. longwire that slopes toward ground and terminates via 500 ohms into a bentonite-enhanced ground system (necessary due to the extremely rocky glacial soil here). A modified I.C.E. impedance matcher is used at the feedpoint. This antenna is oriented toward PNG/Indonesia, and moderately outperforms the rectangular loops on tropical band PNG & Indos about 75% of the time. When DXing other target areas and/or frequencies, the loops are superior.
BTW, the rectangular loop system also uses the same