Got it, thanks. I'm having some fun understanding timers and prescalers now, thanks to the Tone library. 
I was thinking on this yesterday, and its good to see this in action.
// if we are using an 8 bit timer, scan through prescalars to find the best fit
if (_timer == 0 || _timer == 2)
{
ocr = F_CPU / frequency / 2 - 1;
prescalarbits = 0b001; // ck/1: same for both timers
if (ocr > 255)
{
ocr = F_CPU / frequency / 2 / 8 - 1;
prescalarbits = 0b010; // ck/8: same for both timers
if (_timer == 2 && ocr > 255)
{
ocr = F_CPU / frequency / 2 / 32 - 1;
prescalarbits = 0b011;
}
if (ocr > 255)
{
ocr = F_CPU / frequency / 2 / 64 - 1;
prescalarbits = _timer == 0 ? 0b011 : 0b100;
if (_timer == 2 && ocr > 255)
{
ocr = F_CPU / frequency / 2 / 128 - 1;
prescalarbits = 0b101;
}
if (ocr > 255)
{
ocr = F_CPU / frequency / 2 / 256 - 1;
prescalarbits = _timer == 0 ? 0b100 : 0b110;
if (ocr > 255)
{