Originally Posted by shelbyfv

From the Kuota website, the 51 would be a size S. It seems that in order to get the 55 or 56 toptube you probably need, a M or even L would be more appropriate. I would ask them to explain their reasoning. You don't want to end up having to use a goofy 120 stem or 50mm of spacers or a saddle pushed back to it's limit.