Well, after about a week I was able to do 50Km, around 33Km/h. On the same route with the gravel bike I usually manage a measly ~30Km/h. I get a 10% improvement due to thin tires. Who knew? :D
I wonder what I can achieve if I change the gearing to a more manageable 50/17 where I can get into the 80-90 rpm range more frequently.