I am a sea kayak instructor in Sydney Australia and regularly have to
pick punters out of the water when they take a swim. A couple of
comments that you can try:

Firstly your lack of upper body strength is not unusual and the other
female instructor I teach with is almost identical to you in
proportions but has fragile shoulders from past injuries thrown in. She
also has problems getting people into boats due to size constraints so
you are not alone in this.

I'm 6'2 and 13 stone and I sure as hell don't try dragging boats over
my kayak to empty them out 'cos they're too heavy when full of water!
And they will capsize you in the process which helps no-one. None of
the instructors haul boats out of the water that way - very poor OHS.
We do it by going into a T pattern (with you at the top of the T)
grabbing the nose of the boat and getting the victim to throw their
weight on the stern to get the cockpit clear of water. This pivots the
boat up and a lot of the water will run out. A careful flick will bring
the boat back down with the cockpit clear of the water so it doesn't
flood again. Talk to the victim so you coordinate your lift with their
heave. Also when picking the nose up do it gently to break the suction
caused by the cockpit - this makes a huge difference in resistance
when pulling up. Residual water can be dealt with via pumps and sponges
when the person is back in thiner boat. This operation is very
effective and minimises strain on you. And with practice can be done
really fast.

Getting bigger people back into their boat is accomplished by a scoop
rescue which sounds like what you are using. You can get them to do
most of the work though reducing strain on you. Come along side the
boat with them between the boats and you lean right over their boat -
really commit and lean your boat on the side. They put one arm over
each boat and wiggle their feet into the cockpit. The key is to make
sure they get their bum right into the seat. This will partially right
thiner boat and then get them to lean away from your boat and their
boat will roll upright. Your job is only to steady them and make sure
they don't tip over too far. Minimal stress on you. Very effective. You
will have to get the H20 out of their boat then but they are back in at
any rate. Pumps and sponges are the go there.

On group management when you are doing a rescue - get them to form into
a tight group and paddle gently into the waves/wind. This keeps them
together and minimses the chance of a second capsize. Also you can keep
half an eye on them. If someone is more competent then make them 2IC
and keep the rest of the group together.

I don't like the sound of 1:8 ratio but it is legal or recommended by
the BCU. We always have an assistant who is delegated to do the rescues
so the group leader controls the rest of the group.

I hope this is useful to you.

Richard Birdsey