The B72 was a four wire saddle with little pigtails in the four wires. It gave the saddle a little springing action, but not much. These were factory installed in Sports up to around 1970, and on Superbes a little longer than that. At some point Raleigh fitted full spring B66 or B66S on Superbes. The B72 is my personal favorite. Photo below. It was discontinued sometime after 2000.

I like that stem idea to keep the saddle bag away from the legs. It never bothered me, I guess my saddle bags only touched a little. But it could be used to mount accessories on a seatpost, maybe a handlebar bag? I'll keep it in mind.

I used a Topeak handlebar bag on a major tour last year. The plastic reinforcing failed early into the trip, the bag took to sagging badly, and it was on a recumbent so the bag drooped onto my legs. I went to a hardware store and found a couple of mending plates to create reinforcing bars. Other than the droop, I really liked the bag, so after I got home, I ordered some 6061 plate and made an aluminum clone of the plastic reinforecement.