SO2 testing

I use titrets for SO2 testing because they are quick and because my batches are small and they use less wine. However, the package insert notes that they yield falsely elevated readings in whites with ascorbic acid or reds with tannin.

Then online I found a power point presentation on SO2 from the Corkscrew Society Meeting by Dennis Henry. In it, he describes an alternative method of testing SO2 in red wines using KOH and two titrets:

You can get a reasonable indication of free SO2 by doing two measurements, but accuracy is limited
Do the first measurement as for a white wine
The end point is when the blue hue disappears
Add a few drops of hydrogen peroxide to the sample and test again
The end point is when the colour matches the end point of the first test (hold them side by side)
Subtract the two readings to get the free SO2

Click to expand...

1. Is this reasonable and correct?
2. Would this also work for wines high in ascorbic acid (for example, citrus wines)?