problem with running in series is that you would likely see temps on each unit increase in succession, with the last unit(s) having the coolant entering at already-high temperatures and offering insufficient cooling. To avoid this, the flow rate (and thus static pressure from the pump) would probably be too much for the C1 waterblocks.
better would be to use a properly-valved system to run them in parallel. A valve on each C1's loop would adjust for any pressure/temperature difference between units.
___________________
___ _ _ _ _ __|
|| || || || ||
Depends on the restriction of the blocks, but I'm guessing they aren't terribly restrictive. Flow rates wouldn't have to be excessively high to get reasonable performance in a BTC mining application. The specific heat capacity of water is ~4200J/(l*°K), or 4200(W*s)/(l*°K). To find out what flow rate you need to move a certain amount of heat with a specific temperature rise, it's just P/(C*ΔT)
So, if we want the outlet temp of the 4th unit (and inlet of the 5th) to be 30°K above the inlet of the first unit, with the first 4 units dumping 4kW of heat into the water (which is way more than you'd actually see) you'd get the following numbers.
Flow = 4000W / (4200(Ws)/(l°K) * 30°K)
Flow = 0.03175l/s
Flow = 1.9l/min
Not sure how many of these dogie has, but it'd be a cool test to do anyway. You wouldn't even need to use that rad, you could just run three of the 360mm ones he sells in series, and maybe a couple of the pumps to generate sufficient head.
*Edit: That's a minimum flow rate to keep the inlet water temperature of the last unit at a reasonable (say 65C with 35C inlet water) temperature. Depending on the block design you might need a higher rate to actually get 1kW per device from the block into the water.