Something like #3... did you try the golden mean proportions for the grill?
Interesting! I used to be a math wiz, but I just get dizzy looking at those formulas now!
I wonder if using a preferred ratio like that would still be appropriate if the speaker face itself doesn't adhere to the same ratio. Another way to say it: Should the proportions of the grill match those of the cabinet?
If it did, the grill would be ~8.5 x 19.5" (cabinet is 14 x 32). Louis' standard for this cabinet is 8.5 x 20, so he was sticking close to proportionate. I don't think I would like the grill covering more than half of the face though. Particularly with such pretty finish (Bubinga... the mock up isn't bubinga, btw. Ebony I think).
Anyone good enough with math to calculate what length grill would result if the width was 8.5" under the golden ratio? I'll google and see if there's a calculator available.
Edit: Ok, found a calculator. If I use 8.5" width, I get 8.5" x 13.753". Now I'll see if I can create a mock up with that size grill. (Fun project!)
Edit: Added fifth option above with golden ratio based grill size.