[bang-on]

<font color='#0000FF'>john,
i have a simplistic approach to this.
eg; 17/35 70mtrs 48% n2
i avoid allowing the fn2 to rise,only fall.if you changed dil to air @ 30mts the fn2 is going from 48% to 67%.
fhe decreases as depth becomes less and o2 increases but i would normally increase setpoint from 1.3 to 1.4 for last stops.
so my thinking is reduce fn2 =less narcs
use same dil for entire dive so no big shifts in fraction of gases
and just let the pp do the work,although deep stops are a must.run a few comparisons on your deco software and see what you think.if anyone has a reason for changing,besides saving on deco i would like to read it.
cheers
barrie