Fermometer on a Sanke

I have my first 10 gallon batch fermenting in a sanke right now. I have heard the larger batch may have more exothermal action. I am using WWL001 which went crazy in the stir plate so I know it is an aggressive yeast. I placed it in a colder room than I normally ferment in but had activity within 6 hours. I would like to be able to know a rough idea of the temp so i can move it to warmer as fermentation settles down.

The wort is a ways down from the top so a wine thief is the only way to get a sample. How would a fermometer work on the outside of a sanke? Any other suggestions for getting a temp of the wort. I am thinking thermowell but may try the pressurized carbonation first, so waiting on the thermowell for now.

Fermometer should work fine. I have one of the side of my corny keg fermenter and it is usually within a degree of inside wort temps. The only time it varies a bit is when I am cooling down inside the fermentation chamber and the wort inside has not caught up yet.

Thermowell with temp probe helps prove all this.