Here's a comparison between Trek Emonda size 54 and Cannondale SuperSix size 54. I don't know your saddle height, guessed 700mm. What I don't know is how much spacers you get at delivery, probably more than shown on the product photos.

* Press the "Swap Bikes" button to swap between the two bikes
* Press "Shadow Bike" to show a dashed representation of the other bike simultaneously
* Press "Fit Delta" to see how the position of the contact points differ
* Click the numbers and edit directly in the drawing if you want to change spacers, stem etc.

https://www.bikegeocalc.com/#14Trek+...5F172.5G30H30Z

As you can see there is despite shorter reach and higher stack on the Emonda quite small difference in fit overall, about 6mm shorter and 4mm higher if you use the same stem. The best solution is probably to size down to get significantly shorter reach, and then make sure you get a good amount of spacers under the stem, and use a riser stem, and perhaps also a riser bar like the Specialized Hover bar to compensate for the lower stack of the smaller frame. A friend has the hover bar on a bike and it's a sneaky way to get higher stack, in terms of looks I think it looks nicer than having even more spacers or rise on the stem.