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Bilbo has given me a couple of excellent pointers over the phone earlier today, and the sites that Joanna recommends are very useful indeed - thank you, girls.
Don't think for a moment that I am giving up with this, but the way forward for the Spring Garden Trellis quilt (which is all sandwiched together and stuck with spray-baste) is to follow my template with the normal 'foot' arrangement.
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I'll leave more ambitious free quilting for when I have (a) a proper free action foot which does not look to be expensive on Amazon and (b) more experience with needle control.