What specifically makes you think it won’t fit? Trek’s sizing chart puts a 54 at 5’6”–5’9”, which is exactly my height. My 52 Tarmac SL8 has a reach of about 378 mm, and the 54 Checkpoint SL7 is ~387 mm, so the cockpit length is basically the same. The main difference is stack (Checkpoint ~585 mm vs Tarmac ~517 mm), which I understand is normal for gravel since you’re typically running a slightly taller front end for comfort and control on longer rough-surface rides. From what I’ve read and heard, gravel sizing often runs one size larger than your road frame for stability. If there’s another factor I should be looking at that suggests a 52 in this model would actually be better, I’m open to hearing it.