Telect's 055-0000-xxxx style adapter plates do not fit into the HDX chassis, the width of the opening was increased to account for the slimmer profile of the HDX splitter housings.  This causes the Telect fiber adapter plates to be too short to plug into the mounting holes, regardless of the spacing across the bottom.  The height of the Telect fiber adapters is ~5”, the hole spacing in the HDX chassis is a little over 6”.