I have used the 3 sisters since the 1970's (??
). I use a modified French Intensive system coupled with companion planting so, each year, I rotate using 4 major groups. I consider the 3 sisters to be 1 group, tomatoes, peppers, basil, and borage a 2nd, a modified 3 sisters consisting of cukes, sunflowers, okra, melon and bush beans is the third group and the last group is actually 2 groups that I combine so that it takes up about the same square footage as the previous 3 (if that makes sense). Group 4a is salad greens, celery, carrots, radish, etc and the other, 4b if you will, is potatoes, horseradish and onions. I also use a group system for autumn/winter crops. As we eat a lot of garlic, garlic is used to border each group. Because all but the mini-pumpkins are so aggressive, the pumpkins are planted at the feet of our grapes (we rotate the row each year).
What works best for me is corn on 10-12" staggered centers, 5x5 min to 8x5 max, with the pole beans planted on the intersection followed by a squash and then repeated. I also string corn along the back-most and front-most edges of the squash. After all of these years, it would be foreign to me not to plant them together
In all fairness, our soil is really rich (years of manure and compost) so we get away with the intense planting. I have found that within a few weeks after planting, the weeds have no room to sprout and the soil stays relatively cool/retains moisture due to the thick covering (especially important in my zone 10 garden where we get 115 degree temps at the height of summer). The beans that are in the middle of the bed are left alone until the end of the season (dry beans) but the beans that are easily accessible are picked green.