Got my first home-made fishing-line-foundationless frame drawn using Dani's recommended method. A beautiful frame of drone comb. The fishing line appears to be intact within the comb, which is a relief.
Interestingly, a frame of (worker) foundation I gave the hive at the same time has been completely ignored. I guess either a) they only want to make drone comb this week or b) they really don't like foundation at all. Bit of both I guess.
I have taken the foundation out and given them another frame of foundationless!