The Converter plugin only works for Weaver II to Weaver Xtreme.
So you could upgrade to Weaver II, then to Weaver Xtreme, and this has been done by a number of people still using 2.2.6.
You also have the option of manually converting settings from Weaver Original to Weaver Xtreme. Before the converter was available, the manual process time required was described as “a couple of cups of coffee”.