Predator 360 reservoir add on

[PRSRVFRSHNSS]

I recently purchased a Predator 360 and would like to add a 50mm x 380mm cylinder reservoir to sit horizontally on top of my radiator. My build is in a Thermaltake P3 which I've oriented horizontally.

Obviously the predator already has a res and pump built into the end of the radiator. From what I've seen online the flow goes as follows for the Predator. Res > Rad > Pump > CPU Block > repeat.
Typically I see people recommending res > pump to be sure the pump is always saturated. In the case of this expandable AIO though the radiator must between the res and pump. Otherwise it would skip the res completely.

My question is would it be reasonable to use the drain and fill ports on the radiator to run a second reservoir and drain and fill through it? Essentially I'd like the flow to stay as is going into the res and to the rad as normal but use the fill plug as an additional out to the second cylindrical res sitting on the rad with the opposite end running out of the res into the fill plug on the opposite side of the rad. From what I understand it would be similar to a Y spitter. Res > Rad + Res > Res 2 > Rad. Not sure though whether it would reduce flow rate though since its as if I'm just increasing the reservoir size.

 

[Mikel_4]

I couldn't find any 50 mm outer diameter reservoir, most tops work with 60 mm. 65 mm (primochill), and 80 mm (koolance).
Adding reservoir to predator saves a lot of time in bleeding and flush/draining.
So the loop would be reservoir > rad inlet > rad outlet > water block > T split ( https://www.ekwb.com/shop/ek-af-t-splitter-3f-g1-4-nickel )+ valve/plug ( https://www.ekwb.com/shop/fittings/extra/ball-valves ) > reservoir.

■ Basically what I understand from you is using additional reservoirs as pass through.
res 1 > rad inlet > rad outlet > water block > res 2 cap (micro tube) or res 2 bottom > T split + plug/valve or quick disconnect > res 1

OR
■ Using additional reservoirs as spare with plug/valve, so when you've finished drain/flush, the spares quickly bleed the loop ?
res a > rad inlet > rad outlet > water block > T split inlet thread - thread to <> valve <> res b dual/triple/quad port cap/bottom inlet (full tank) ~ dual/triple/quad port cap/bottom outlet valve <> T split outlet thread > res a