I used my own version of this, I toy'ed with the idea of using my Ceramic coated AST tank from my RX7, never got around to it though.

We had my resevior in the hatch (eg hatch) and with the extra hoses and the resevoir, i went from 1.5 gallons of water to 5 gallons....now do you really think its easier to cool 5 gallons, when a resevoir does nothing but hold water and heat? I use an 8gpm pump and with the resevoir, once the temps would began to heat up...they just kept going up and the would level off at like 160-180.
Now that my exchanger hold 90% of the water, it is always cooling.

I hope i explained that the way i wanted?