I am using the same heat exchanger with 1/2" ports.
I was aware of the risks of a single wall exchanger when I bought it, but was cheap and wanted to make sure it would do the job before spending a bunch of money. I did put a check valve in front of it and was only using it for shower and not drinking water. Although with some current changes it can supply hot water to my sink now.
With that said this heat exchanger has no problem heating water, in fact it works so well I installed a tempering valve after it to keep from scoulding people with 145 degree water. It has been in use for a year now.
I plumbed the coolant lines it to the back using silicone heater hose, I used 1/2" copper to go through the floor of the van and to connect to the exchanger. My entire water system is inside the van for winter use.
Idon'thave rear heat so to 'T' in to the front heater hoses and to keep the coolant from flowing through it when not needed I installed this bypass valve:
It is vacuum operated so I used this actuator to operate it from a standard 12v switch:
So far everything is working great.