2mm header (SEO shenanigans)
Its a simple hack to use boards with 2mm spacing headers with the usual 2.5mm headers, the pictures are worth a thousand words. You can use this with your most esp8266 or xbees.
Strip a wire, and give its a twist.
Insert it from the solder side
Do it again as per your need
Place the 2mm header spacing board, move the wire with pliers where they need to be soldered
Solder the 2.5mm headers
Use them as daughter boards.