I'll second that and the RD course is good fun, bit also with a serious side on teaching you techniques (see, size DOESN'T matter!).To be honest old mate if your able to dive then your not to small to do rescue bodies in water really weigh very little so it's purley techneque. you really ought to just enrol her on the padi rescue at least to give her a fighting chance.
Attaching you to a lift bag is probably not a good Idia. It will just create more confusion in the seperation of the two of you. as for the extra weight then yes best you loose it as it'll at least give your hart a chance.
Go on do your wife a favour loose the weight and get her to do the rescue course she'll enjoy it really. Oh and she'll probably be really proud of you making the effort to loose the exesss. :teeth:
As from personal experience, I've done practise and real 'rescues', largest one was a gentleman nearly a foot taller than myself, and so long I knew how to apply the techniques, I had confidence in myself.
It may then be a good idea to do the RD course and then when on dives, practise some of these techniques, as you will never know when they are needed.