Piping question for Quietside boiler / tankless install..

Timco

So I am installing a Quietside 120 in my own home. One of my two 40 gal went down and I just did not have the heart to simply plop another tank in there. I need space and want the high-efficiency as well.



My house is about 1700 sq', maybe 80k heatloss and I added some rads in the unfinished basement so including that maybe 100k. I have a front & back zone.



With 3/4" taps from the boiler, since I am zoning and may wish to add a zone some day, wouldn't a 2" manifold / buffer tube under the boiler with a primary pump be the best way to keep flow up? Then maybe 1" manifold off that for supply & return and mix in the buffer?



Thanks,  Tim