The most common variegated form, 'Aureola', is pretty slow to establish pretty much anywhere :-) I plant several in a close grouping if I want immediate impact, otherwise I allow several seasons before I expect them to fill out much.

I've seen 5 and 10 gallon mature Hakone grasses at local nurseries, but they are rare and expensive. You might ask a local nursery if they can special order them for you.

Hakonechloa is noted for being slow to establish and expand. IME, all cultivars will take sun quite well as long as the soil is sufficiently moist - it doesn't care to dry out at all. The species is the fastest to establish, 'Beni Kaze' and 'Albo-striata' somewhat slower and 'Aureola' and 'All Gold' quite slow. I planted a clump of 'Albo-striata' in a container planting last summer and by the end of the season, it had taken over the pot with a huge root system. I guess that's testament to the benefit of a loose, well-draining soil, additional fertilization and frequent watering.

Thanks, gardengal. I'm going to see if I can get in there and slice it out with my garden knife, without having to dig out the entire plant. If it's on the edge of that clump : I have not examined the base that closely. Unless you think better results would be obtained by digging up the whole plant and dissecting it. Of course, it's the plant in the most inaccessible location in this new bed.