Found this: http://wirelessjoint.com/viewtopic.php?t=98
Seems Cradlepoint makes a MC400-600M-C-AT with dual SIM support and the EM7511 inside, but locked to AT&T and double the price (in which case one could just buy two modems and use both SIMs in parallel!)
The EM7511 advertises Dual SIM Single Standby support. But the devices that accept it only have a single SIM card slot.
thewirelesshaven suggested using the "Mini PCI-E to M.2 (NGFF) Key B Adapter with Top SIM Card Slot" and the "USB3.0 To Mini PCI-E Adapter Enclosure With SIM Card Slot" together ...
From reading here, I gather than https://thewirelesshaven.com/shop/antennas/700-2700mhz-15dbi-4g-lte-directional-antenna/ is the best antenna to use? Should I get a pair of these, or does the AUX antenna not matter as much?
I'm using this enclosure: https://thewirelesshaven.com/shop/pcie-m-2/m-2 ...