I found a sweater pattern I would love to make, but it calls for Red Heart Grande and size US 19 needles. The gauge is 6 sts= 4". I would like to use a regular 4 ply yarn (two strands?) either acrylic or cotton. Is that possible?
Red Heart Grande is a bulky yarn
which is generally a 16 ply equivalent or heavier.
To use a 4 ply you would need 4 strands rather than 2 and even then you would need to knit a tension square to make sure that you could match the tension
specified in the pattern.
Depending on how close you get, you may have to use a bigger or smaller needle size
(US 19.0 is equivalent to 15.0 mm).