Talking about frame angles goes way over my head.
The Paddy Wagon has standard road bike geometry and handles like a nice road bike. The 73 degree head angle will steer a little faster than the 72 degrees of the Flyer. The steel frame does flex, but then it is a steel bike with small tube diameters.
The geometry of the Paddy Wagon makes the ride and the flex is part of that. The (cheap) steel frame on mine is offset by carbon forks and custom handbuilt wheels. I ride it almost every day and will take it out for a 30 mile club run tonight. Full SKS P35 mudguards and all.
Without the rack, mine is 9.2 kilos. It “rides” about a kilo lighter. I as thinking of upgrading the frame to titanium (same geometry), but a new 520 frame would be almost as nice.
EDIT My PW has single eyelets on the back for mudguards and a rack (mounted from each side with short bolts. No rack mounts on the seat stays, so I use a seatpost collar with two mounting points. A tubus fly would also work fine.