There is no "wrong" answer to this. It's really depends on the look you like and the density of the quilting that you are planning to do. If you are quilting densely, then a finer thread would be good. If you want the quilting to stand out more, then a thicker thread would do nicely. One upon a time there was a myth that poly would "cut" your fabric. That really doesn't happen. I always use poly unless hand quilting. You might try making a little mini-block and test out different combos and see what effect you like best.
Martine has brought up a great point about single run versus double run stitches. I really have enjoyed quilt-as-you-go, but do not like the quilt blocks that do not actually quilt through all 3 layers (top fabric, batting, and backing). Unfortunately many beautiful quilt blocks are not really designed for QAYG to be quilted through all 3 layers. I usually end up re-digitizing these blocks so that I can stitch the embroidery design, I create outline stitching for that embroidery design and then the quilting with run stitches will stitch. I do not use any stabilizer, but hoop the batting, float the top fabric and float the backing fabric...or if the finished block allows, hoop top fabric and batting, stitch the embroidery, add the back fabric on the back of the hoop and then stitch the quilting design. The wedding quilt I did for my newhew and his new bride was all done as QAYG, including the borders. All the blocks were done and then I joined them on the sewing machine...then I added the borders made to fit the sides of the joined blocks. Looking forward to seeing what you do... What I do not like seeing is the back of a "quilt" that does not really have any real quilting through to the back which is what most designers/digitizers do with their blocks... Just my personal peeve I guess...
I am in the process of sewing four blocks together which have the border sewn. Then quilting all three layers together in the hoop. I will make a test block before starting on the quilt. I did not even think about floating the fabric. Thank you for your reply.
Quite a number of machine quilting designs are double run to keep them continuous. I use 40 wt cotton for those. The single run designs. might benefit from 30 wt, makes them just that bit sturdier. Question might be which is which - some designers give that info. And being able to have it 'stitch' out in your software- if you have it - porvides an answer too.
I like to hoop water soluble stabiliser and pin the sqares on top, whether it is quilt as you go or a finished quilt. But working QAYG is a lot simpler than manhandling a larg(er) size quilt.
Have fun experimenting!
Thank you for your information. I have seen 40wt cotton but never thought I would need it. I appreciate your informations
To ensure the quilt will stand up to years of use and washing etc. the 30wt is thicker and would hold up better. Look forward to seeing the quilt when finished Pam, good luck, love Chris