I’ve got one! It’s been great for me. It’s currently got Marathon tyres, ‘guards, rack and dynamo lights but still feels light and fast. Towed our daughter to the beach in a trailer on Saturday afternoon (disc brakes and flat bars very helpful for that) and kept up on a fast 50 mile club run on Sunday morning.
There’s a bit of space around the P35 mudguards so I think you’d get some 40mm tyres in there, though probably not much more. I’ve done an off road commute a couple of times over the South Downs and it was fine even on the 28mm tyres.
Frame & forks seem very light and well designed too, fork even has internal routing for dynamo cable.