I freq use fleece as the backing of a quilt ( I quilt for older ppl that tend to be so cold all the time) I freq use double knit as batting... normally more in a quilt as you go type setting.... but I have done an over all batting of double knit... I try to remember to quilt it a bit heavier to keep things from stretching and getting funky..
Yes, I grew up with only old blankets and quilts used as batting in the North central Texas area.... I was well grown before i knew batting even existed.. lol