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The 100/2 is not listed as recommended for the 2Xa. That is not to say it won't work, as the table may pre-date the release of the 100/2. However, noting the notes/precautions:
"Trying to use this converter in combination with other lenses than those named under 'Characteristics', specially lenses with protruding rear elements, may seriously damage both the lens and the converter.
When focusing screens with a split image and / or microprisms are used, the center of the viewfinder may darken. In this case focusing must be done on the matte ground surface."