Gravity RE-Conversion---Any advice appreciated

Vitodens simply attached directly to the gravity system with a differential pressure bypass valve between supply and return.

TRVs keep the flow requirement down; gravity piping keeps the piping head loss zero (well zero for calculation at least) so the only real head loss in the system is the TRVs themselves--and even then very little at the typical ounces of flow required through each. Built-in circulator has ZERO problems providing sufficient flow in any weather and any reasonable TRV conditions. I've raised TRVs on different floors for more than half of the EDR sufficiently to get wide open TRVs and with a near "starvation" curve--ALL rads heated rapidly and evenly. With a higher curve I've raised TRV settings for 90+% of the EDR--rads still heated rapidly and evenly.

The "buffer effect" I described is based on observation and measurement of the Vitodens system. The "damping" effect is based on both the old system and the Vitodens. ONLY thing that changed between old and new is the boiler itself--I even ran it at the nearly same reset curve for most of the first year.