Arduino should be modifed to drastically reduce its power consumption. This applies both to Riki and Dolphin: the Arduinos should be interchangable between the two boards, it's just necessary to upload the appropriate firmware.
The starting point is an Arduino Pro Mini board, 3.3V 8MHz version:
Specifically, it's important to remove the voltage regulator (A), since we're going to use an external one anyways. It's also really important to remove at least the power LED (B) or its resitor (removing the resistor will still disable the LED, and it's probably easier), to avoid it wasting power. It's the recommended, but optional, to remove also the pin 13 LED (C).
Removal can be done using a cheap desoldering iron, or even with a soldering iron: after all, it's just necessary to melt the tin, then the components should fall off the board easily. It's also possible to use a cutter to just cut the contacts, but it's important to be careful ad avoid slipping, to avoid damaging other lines or chips.
After removing the useless components, it's possible to solder pin headers. We reccomend soldering straight headers on all pins (including A4 , A5, A6 and A7) and 90° headers for the FTDI pins (the 6 pins going from DTR to GND).
In the end, Arduino should look like this:
