A decent wine protocol.
To be valid comparisons, the wine in each glass being compare MUST be from the same bottle. Even in bottles from the same case, there are frequently noticable differences from bottle to bottle.
Neither of magnetic coasters suggest that the time to get their benefits exceeds an hour.
An hour isn't an unreasonable amount of time for a red wine to decant.
Keeping all the above statements in mind......
For each bottle of wine, decant it into 2 identical decanters. Sit one decanter on a magnetic coaster and the other on the counter. On each subsequent bottle, alternate whether the magnetically treated decanter gets filled first or second, to eliminate any small chance of preference for the top or bottom of the bottle. Do this for at least 4 bottles, the more the better.
Pour a small glass from each decanter for multiple tasters. Eight tasters should do pretty well. When I say, a small glass, I really mean not much more than a good swallow for each taste. You should be able to get 2 or more tasting rounds out of each bottle. Have the glasses simply marked 1 and 2. Which glass that gets the magnetically treated wine for each taster and each round of tasting is picked at random and recorded. Have a 3rd party (who isn't aware of how the wine was distributed between the glasses) present the wine to the tasters. After the tasters have done their tasting, they answer the following multiple choice question.
"Comparing your glass of wine 1 to glass of wine 2...."
"a) You could not tell any difference between the two."
"b) Glass 1 was better than glass 2"
"c) Glass 2 was better than glass 3"
Then compare the tasters' answers to the dispersing records. Do the results line up better than would be expected by chance? Even if they consistently choose the magnetically treated wine as inferior, that would be a surprising result. It would indicate that the magnet at least did something. Or, even consider that one taster would pick the magnetically treated wine consistantly better, and another picked it as worse, that would be worth further study as well.
Then, it would probably be a good idea to rerun the test in the same manner, but eliminate choice "a" (could tell any difference) and see if forcing them to pick one or the other gives any better results.
It would a good idea to try to use the same tasters from one session to the next. By collecting more test results from each taster, you could find that if there was a difference, only one or two of the tasters had a good enough palet to discern the difference.
Run as many sessions of this as you can afford. If even 1 taster in 8 could seperate the wine by taste even 75% percent of the time over 6 or 7 runs, that would worth further investigation. Perhaps if you get one or two tasters that show promise, do additional testing rounds only with them to see if their tasting accuracy can remain statistically significant over the long haul.