Is 60mm big enough? Start - Schwalbe Professional Bike Tires
Heh, just a bit too big, i’m running 60mm fenders that just fit the the frameset with a mm or 2 spare gap.
I can fit 50mm Schwalbes sans fenders, haven’t tried with them in place.
I reckon anything ~300-400gms with puncture protection, no knobbies, between 38-45mm is what i should be looking for. IIRC I found some Paselas in the States that should do the job.