Thermometer on a pot still?

[Pamulli]

Maybe this should be in the novice section, but since it is design related, I thought I'd post it here.
I'm building my first pot still out of a stainless milk can and wanted to know about incorporating a thermometer. I don't see thermometers in a lot of pot still pictures I've seen on here however it seems like it would make it easier for a newbie to have one? If I do want to put one in, does it matter where? Can I put it in the top of the milk can or does it need to go in the column or does it even matter?

Thanks for the advice