Some of the nicest sheets that I have ever had were 60/40 - they washed and dried really well and were so soft. But, on a quilt that my aunt made, she used some poly/cotton - don't know the percentage - and it "pilled" a bit - sort of a bumpy feeling. It may have been a higher percentage - maybe even 50/50. I don't think that you will have a problem though. However, if the other sheets that you used were not the same percentage, then you may have a different shrinkage.