I did find
this older post from a gardener in Maui. It seems to indicate that the growth is expected for a Japanese moschata: vines about 15' long, several fruit per plant, small fruit in the <5 # range.
Of course, Maui is wildly different in growing conditions from me, so I would love personal accounts from anyone who has grown it in a less different location.
Also, the blogger calls it "Sweet Kikuza", but it seems that it's the same variety as what is being sold as "Kikuza" today, both tracing back to Oriental Seed Co. of SF in the early 1900s.
The reviews at Baker Creek are all over the place and not very helpful.