Lots of interesting debate in this thread on air flow through the cabin heat exchanger but has anyone every determined by temp measurements if the cabin heat exchanger itself is actually getting enough coolant flow through it to get it good and hot?

My cabin heater kit is the one sold by Kitfox with the coolant flow tee'd off the main radiator hoses and with the two computer fans. However, it just doesn't seem to send out much heat into the cabin when it's 30-40 F ambient or colder (in Northern Illinois). In contrast my Toyota's heater will drive me out if I let it go.

Although the two computer fans do seem to push some air through it that I can feel, its not exactly a hurricane and its just not very warm. I've sealed up air leaks around the firewall and elsewhere to minimize cool ambient air ingress into the cabin but I'm wondering - Is there a way to modify the coolant plumbing somehow to potentially push more coolant flow through this cabin heater to get it hot without negatively impacting the coolant flow to the cylinder heads? The following diagram crudely depicts my current plumbing:

Scan 5.jpg

My CHT seems to always hover around 180 F so it seems that my cylinder heads are getting plenty of coolant flow. Or do I need a coolant thermostat or something else to raise the overall coolant operating temp?

Does anyone have the standard Kitfox set up that proves its output is more than adequate? If so what do you attribute it to? Any thoughts are appreciated.