FMC-compatible Molex connector?

[aylons]

Hi, everyone!

I was trying to prototype a simple FMC LPC mezzanine design when I found that Molex also supply FMC-compatible SEARAY plugs. Great, because Samtec is very hard to find at Digikey or Mouser, and the Molex part is in stock at Mouser

However, I'm utterly confused by Molex documentation: the part page says 400 loaded circuits, however, the FMC LPC only has 160 circuits. To add to the confusion, if you take a look at the last two pages of the drawing [1], it seems that there are only 4 rows, which is consistent with a 160-circuit connector, assuming the usual 20 columns. This would be footprint-compatible with the tradicional Samtec part, however,  I can't find any explicit mention to the number of columns for this part number and, of course, I'm still more confused.

So, has anyone here used Molex 45970-4305 as a substitute for Samtec ASP-134604-01 or anything similar? Is it really footprint-compatible? My main concern would be having some vias below the footprint shorting with the unused solder balls of the FMC connector, connecting an unrelated signal to the carrier.

Tried to send an email to Molex, but no answer so far.

Thank you!

[1] If you pay attention, the first 4 pages of the PDF are a document and the last two are another, different document.