I have a 58 Checkpoint SL after my Crockett frame was generously warrantied and I upgraded a bit (trek is the best). I got the carbon frame for the ISO rear, as I planned on using the bike an endurance bike too.
After spending some time with it, I wouldn't do CF again. The CF frame has nicer cable routing (hosed cable end-to-end is nice for sandy areas and crossing water), more bottle cage bosses, uses a seat mast, and the Di2 battery compartment (which is great for tube storage), but it rides the same as my basic Emonda ALR and my Crockett (with Specy zigzag seat post) on the same tires/wheels at 85psi. On rough pavement and hitting potholes, there's no difference. In contrast, I was getting abused on my Crockett on road tires until I bought the SBC zig zag seat post. I'd save the money and get the 300-series ALR frame and a fancy seat post (if needed) if I were to do it again. The seat mast is a particular PITA as I need a bit more setback and can't just change the post. I don't have thigh gap and my legs also rub the wider CF tubes.
I've got 43mm tires on there, and I wouldn't go over 45mm after having a look at it. You can run a bit larger, but I managed to sand the paint off my old bike running too large of tires and 43mm manages on soft sand.
Tip: You can be REALLY aggressive in shortening the cable housing between the bars and downtube guide. There are some complaint about it being annoying and hitting your leg, but I've got it internally routed on my bars which open up close to the stem and just the bare min of cable - it's nice and clean. It can rub the paint, so put a clear frame protector sticker there.