Ok, so I got around to it pretty quickly. I have so far completed about two and a half of the 16-row repeat on the pimlico shrug, this time using a 4.5mm circular needle. I'm enjoying the knitting, it's pretty mindless and seems to be what I need just now. I also have the eyelets mastered and although I'm not entirely certain that I am doing them 'the right way', I am happy with the way that they are turning out.
I plan to knit eight repeats and then take the fabric off the needle and block it out (with a safety line in there to prevent unravelling of course!) to get a better idea of eventual size and shape. Then I'll clasp it all together with my trusty mini-hair clips and make decisions about whether any further knitting is required. I am aware that for many people this garment turns out way too big so I am going to be very conservative in the sizing, although of course I will only be able to change how long it is (from neck to waist) and not how wide (those 161 stitches are remaining 161 stitches whatever I do).