If youre using it to harvest my corn it will handle it just fine.Second year in a row of zero yield.Id go with a 4 row myself.The six row is a little to much weight plus the F doesnt have quite enough capacity for a six row.
I know of at least 2 that are pushing A630 corn heads. level running, yields in 140-150 range at best. I would question that much weight on front of machine, esp with smaller tires. My feeling would be in good corn an F3 would get a "tummy ache" in a hurry. It would do it, but you would be measuring speed by "coffee cup method". Set down coffee cup, come back in 15 minutes and see if it has moved.
i'm only guessing, but you can buy the 6 row rather cheap. good deal. buy it for parts for the 4 row and enjoy the coffee while it's hot. bin capacity and length of rows would be another consideration. we used to run g's with 6 rows and got along fine in 80 bu. corn, rear wheel wheights and calcium in fat back tires.
Owned an F and an M2, here in Iowa the 4 row head was pushing the cleaning limits of the F and my M2 had a 6-30 and it was traded because low cleaning capacity and sidehills with the 6-30, too much yield for that size machine, not the M2s fault. My N6 hyper'd is 6-30 and runs 6-7mph in 200+ bu corn every years and has room for more, nothing seems to effect its capacity. Yield and slope are the greatest effect on a machines capacity as to head size. F series fly with 4-30 or 4-38 heads. 6 rows are really pushing its limits.