I have not done SFG with the Three Sisters, but I have done the Three Sisters Garden.

I did it in previous years with hills (3 foot diameter) separated by about 5 feet on center. The corn (6-8) went in a center ring ~ 1 foot diameter. The beans (10-12) went in a ring outside the corn diameter ~ 2 feet, planted about 2 weeks after the corn. The squash goes in the outside ring, the side of the hill, planted at the same time as the beans.

Some will tell you that the beans will rip the corn out, some will tell you that the beans will wrap too tightly around the corn. The Native Americans developed this method, so it DOES work. The issue is plant choice! The traditional method was for dried corn, dried beans, and winter squash. This was how they made it through the winter. If you want to use sweet corn, green beans and summer squash, know that you are making adjustments to the method. Expect to encounter difficulties.

For myself, I did all three variations, and had some success. Enough that I have continued to try it. I got about 12 ears of sweet corn out of only 4 hills. I got a good supply of beans, for as long as I continued to pick the pods. I stopped picking the pods once the corn was finished, as I wanted to plant NEW things in their space. The zucchini that was at the bottom was AWESOME (as zucchini usually is)! It just kept coming and coming. Eventually, I got tired of zucchini. I pulled it at the same time as the corn and beans, so that I could plant some fall crops.

It works, but be prepared for some bumps along the way.

As far as doing it with SFG this is what I would do. Plant them in long rows. 1' x 4'. Plant in the center of the 1' - but...Try 3 corn stalks (plant 2 or 3 seeds per spot, and thin to 1) per 4 sq/ft (plant them where the dividers go). Plant 4 beans around each corn stalk, and thin to the strongest two. Plant squash in the ends of that 4 sqft row. Then repeat for as many row as you want.

More rows will give you a better chance of germinating good ears of corn.

You can plant corn closer than 1 foot, as close as 6 inches. The soil just has to be ready to handle that much corn!

Does 2 sisters count???

I planted them 12 inches x 10 inches apart and in between I planted both kentucky wonder and scarlet runner beans. I got lots of Scarlet runner beans and very few Kentucky wonder beans.

I planted corn and beans together.

They did really well

UNTIL....the evil Newfoundland Wind blew the corn over

I staked them back up

and ended up getting some smaller cobs off them,

And here is some more corn and some of the scarlet runner beans...

Oh and the lost sister wandered over to the hill garden but atlas she missed her sisters and never gave me a pumpkin :(

Oh and a really good reading about this straight from the mouth of an native american woman Buffalo Bird Woman.

I have this on the back of the throne in the reading room and have read it from cover to cover.

Great stuff!!!!

Here is a link that might be useful: Buffalo Bird womans Garden