What size? Chests up to 42 high/wide should be migrated. There isn't a way to migrate arbitrary lengths of chests, so I had to make decision where to make a cut off point.
There might have been some problem in 1.1 because only chests larger than 4 were not migrated. And looking into mod setting you listed "1xN 2xN 3xN 4xN" (with mirror enabled) as whitelisted chests. So it makes sense that 5x24 chests are not mergable. Include "5xN" and you should be fine
