this has certainly been done before, for touring setups as well as real racing
John Tomac did this setup when riding for 7-11
For sizing and setup I’m leaning towards the Medium, although what is your stem length on the Epic currently? And what is your stem length on the Tarmac?
Is there suspension on the front end and how much travel. What size tires you gonna run?
Note photo below from BITD, he changed out to a rigid fork as the suspension fork was too wobbly and caused some interesting handling with lower/longer weight distribution. I think the rigid fork also had a longer axle to crown length which helped with handling too. I always argued that this frame was too small for him too, imho.
