Ok, Here's one plan.

Buy 4 of those 19 tooth finger pickup dual sprocket setups. With planter seed tranny set at 33,000, then that should get you to 48,642 population (28 divided by 19 = 1.474 ratio; 33,000 x 1.474 = 48,642) Base rate for those 4 rows (for math purposes)

Now, that 48,642 number is close enough to be roughly half way to desired 44,000 and 55,000 numbers, so we can now overdrive and underdrive, to get close.

Let's look at the 19 tooth DRIVE sprocket on the hex shaft, for those 4 rows. (see photo)

If we modified two(2) of those down to be 17 tooth sprockets, then 17 divided by 19 = .895 ratio. population of 48,642 x .895 = 43,535 population (close to 44,000)

Next, if we modify two(2) of those up to 21 tooth sprockets, then 21 divided by 19 = 1.105 ratio. Population of 48, 642 x 1.105 = 53,749 population (close to 55,000)

Now, during this discussion, it reminds of a picture (I can't find it, yet) that someone showed that they had installed a "jackshaft" on their parallel arms(or right in front of seed boxes), to straighten out the chain scenario of when a person uses Surestop clutches and JD Heavy duty downpressure springs. This has me thinking, once a person adds a jackshaft, then sprocket teeth changes(ratios) become easier. I believe the guy used a short chunk of 7/8" hex shaft, for the jackshaft.

(JD 19 tooth drivers.jpg)

(parallel arms_in paint program.jpg)

JD 19 tooth drivers.jpg (37KB - 245 downloads)

parallel arms_in paint program.jpg (61KB - 267 downloads)