Thanks for the reply Box - do you have any tips as to which extensions might be suitable?

Hi -

Does anyone out there know how I could 'fill-in' the two indentations in these shapes (see image). I'd like the curves to follow the form - if you see what I mean... I've tried many diffent methods to solve this but haven't been able to so far. Perhaps there is a plugin which could help? All suggestions gratefully received.