Floats and doubles are the same.
I think the point is that floats and doubles are not the same. The arduino turns doubles into floats so when you are using an arduino they are the same.
I presume he wants some way to make them how doubles normally are (8 bytes ~15 digits).
double on arduino: http://www.arduino.cc/en/Reference/Double
I'm still unsure as to a possible way to do it though.
Mowcius