Here are a few ways to improve stretch capabilities with plastisol inks:
1. Ensure there is a sufficient ink deposit. If the ink film cracks when stretched, it is a sign of improper cure and fusion.
2. Most ink manufacturers have stretch additives that work very nice. It’s important to note here that it’s always a good idea to pre-test garments before a production run as well.
3. Use a fast-fusion clear as an under base. These clears have tremendous stretch properties and allow top layers to achieve maximum stretch as well.
http://printwearmag.com/tips/achieve-stretch-in-plastisol-prints