Hi FvM,
If you check the HDMPs datasheet; your data is deserialaized to 16 bit words, system has mux/demux of 16, & with an + 4bit header has the 20 bit words...
Exactly thes muxing was the reason for my proposal of ca. a month ago. we applyed a extra 4x mux/demux too, I remember yet & 40 MHz for the 16 bit datawords...
At this time I can not tell more over their_sorry, than I think too, naowadays are (hopfely) more similar or better components to find or realized.
Regards!
k.