haha I was looking at that breakout board myself, with a battery this size I'm thinking i would have to remove the connectors either way. so you're thinking of separating the two with a piece of perf board essentially?
the battery is 60mm x 36mm x 7mm. if it will fit its going to be tight but its what i had around, not opposed to buying something new but wouldn't mind the crazy battery life.
neither specifically states it but the language in the data sheet would have me believe they both do.
these are them
https://www.adafruit.com/product/1904
and
https://www.adafruit.com/product/259
i know I'm a little late to the party but I'm about to do this same mod myself. would it be possible to get a schematic. I work better with visuals lol. thanks