There must be a trick to it but I am not coming up with it. I want to add external antennas. I have worked with Hirose style u.fl/IPX type connectors before (its easy once you get the hang of it) and have everything I need as far as soldering. My guess is that a specific tool must exist, one that frustrates the designs of those like myself who would always want to look behind the veil, so to speak? Anyway, I don't want to break it.
Edit: There is a good video on soldering u.fl on YouTube "Hand-soldering u.fl connectors" by user "TwistedPearAuio"
Also, the UART looks interesting. Is it a 3.3volt UART console? Will add a header and some short wires to a DB9 or similar on the outside (in the USB cutout if there is one) if it is. If antenna jacks are added they should both be anchored in an appropriately sized piece of metal thats attached securely to the case. Putting female SMAs or whatever into plastic wont last. You don't want to be plugging in and removing Hirose / u.fl connectors, they are not designed for much use, they have a very limited number of uses (30?) in them.