Thanks Markfletcher007, that is a handy chart and I never realized these things really mattered. I think I will get a 2.8 and a 2.4 and see if i can notice any difference between the 2 and go from there.
The vivi nova i bought has a 2.8 in it right now.
And how are you finding the 2.8 head?
Ok your voltage range is 3.3 to 4.8 so if you use the chart to find the sweet spot it should help
Would suggest a 2.4 or 2.8 based on the sweet spot range on the chart although 1.8 should be ok dependent on your setting
For some reason I can't access the chart :-( my vamo is arriving tomorrow so would have been handy...gah!
What is it doing when you try and open it?