The goal in pattern making is not only to make a pretty pattern but to make a strong one that can stand up to the rigors of flipping, framing and hanging.
Curved lines are stronger than straight lines. Glass wants to break straight so when you make it curve it makes the piece stronger. When you make a straight line all the way across the piece, it creates a weak spot. Some of these are necessary (i.e. horizon line) but I try to keep them to a minimum. If you want a lot of straight lines, like a double boarder, stagger your cut lines so that none of them go all the way across. Even putting one piece across a straight line can make the piece much stronger, but multiple pieces make it like there wasn’t even a straight line.
If your design requires multiple straight lines a great way to add strength is to add strong line in between your pieces so that it is perpendicular to the straight line. This will reduce the risk of folding on the straight line.
I would be happy to help if you have questions designing stained glass patterns.