I bought a previously loved Ratio Six brewer over the weekend. So far it has matched expectations and I am happy with the purchase. For reference, I also have a Technivorm, an OXO Barista Brain (the big one), and a Bonavita. Out of curiosity I tried to use a Chemex with the Ratio and realized it doesn't work. The Ratio carafe has a magnetic bottom which activates the brew cycle and turns it off when the carafe is removed (safety). I ordered a fairly strong, quarter size magnet on Amazon and that did the trick! I just place the magnet under the Chemex or any other vessel/carafe which activates the brew cycle. The stock carafe and filter holder/silicone ring seem to work best for taste and heat retention, but this hack just adds another dimension to the possibilities.

Thanks for posting this... was just thinking of doing the same thing!
Were you able to place the Chemex so that it fits centered under the shower head? (I know their own glass carafe sits a bit askew because of the way the head is a few mm closer to the body than the base is). And is that the 6 cup or the 8?