We'd been discussing the types of parachutes used by VIIIth
AF crews, and whether they were worn or not in the heavies.
I've just retrieved a copy of Roger Freeman's "Mighty Eighth
War Manual," which goes into great detail on all manner of
operational procedures, equipment, weapons, bases, etc.
Here's most of his section on parachutes (I've left out the
section on fighters):

"VIII BC groups were equipped with five different types of
parachute during the early days of operations. These were
seat-pack types, S-1 and S-2, back pack types B-7 and
P3-E-24 and a few US chest packs AN 6513-1, a new design. A
study carried out in January 1943 showed that most B-17 and
B-24 pilots and co-pilots wore seat type parachutes;
bombardiers, navigators, waist and radio gunners used seat
and back types. Very few turret gunners found they could
wear a parachute while at their stations. B-17 tail gunners
used back types. Because of the fatigue caused by the
additional weight and interference with movement, half the
men who could wear parachutes did not. The parachutes were
therefore placed at the nearest handy spot, crew members
trusting that they would have enough time to retrieve them
and get into the harness, although pilots and ball turret
gunners took a very fatalistic view of their chances if
forced to bail out. With the exception of the chest type,
all these parachutes had attached harness requiring three or
four separate actions to attach and detach, without any
provision for attaching individual life-saving dinghies."

"Pilots wearing seat packs found that they could not get out
of their seats without first unbuckling leg straps. Even
the quick attachment AN 6513-1 chest pack parachute was
found far from satisfactory, chiefly because its fixings
were not sufficiently strong. To improve the situation, in
June 1943 the 8th Air Force Central Medical Establishment
recommended that all bomber crews wear the RAF quick-release
harness and observer chest-pack parachute until better types
were forthcoming from the USA. The advantages were that the
harness could be worn at all times and in one operation
could be quickly and completely removed; both parachute and
dinghy packs were quickly attached to it by simple snap
hooks. Some back-pack parachutes were retained for special
purposes and the US chest pack, AN 6513-1, continued to be
used until sufficient Observer packs were available. Also
the harness for the aN 6513-1 was modified for quick
attachment and many canopies from back and seat packs were
repacked in the British chest packs."

"RAF Observer chest packs were supplied to all 8th Air Force
bomber groups until a new US chest pack with nylon canopies
was received in 1944. Despite successful projects to modify
ball turrets to enable gunners to wear a back-pack, no
similar move was made in production and escape from this
crew station remained the most precarious."

Guy