If you're required to use the 10% rule (i.e. generating a saturation curve) for determining intensity, the rule states that intensity is the value of the arc height at t1 when the doubling of that TIME (t2) results in a 10% increase in the arc height. This, of course, relies on the flow rate to be constant.
The idea of altering the flow rate for a given time is interesting but not recognised that I know of.
Also, note that the doubling of time is only required to satisfy the 10% rule between t1 and t2. Your acquired data points can be virtually any value as long as one of them is at or beyond t2.
