My problem now is figuring out Where to install a tank..
This evening, I went down and looked at the back of my boiler.
There a 3/4" nipple sticking out (on the rear left side) that has a T&P valve on it.
I think it would be a quick install, if I skipped buying a tank (HW heater).
Just build a little shelf for the A7, beside the boiler and run the HX loop into the 3/4" hole.
I can install the T&P elsewhere.
If the HX loop was fed into the rear left side (3/4 from bottom), it would intermingle with existing domestic HW HX coil..
The water jacket hold 72 gallons of blackish water..
The main problem with the idea is the thin insulation, and leakage up the chimney..