I have heard from a good source that the rings that Image sells are chrome. Chrome rings are NOT compatible with chrome bores.
While dual rings are better for our application, the single ring design is proven to work good in the 550. As long as the ring and bore materials are compatible.
In my opinion you have 4 options:
1. find NOS pistons and rings
2. have your cylinders nicasiled
3. have your cylinders steel sleeved
4. Use the other single rings & pistons that are available that do not have chromed rings. (unfortunately these rings will not fit on the pistons Image sells)