You shouldn't be using the sides of the racket And increasing the length of the main vertical strings has its advantages.
Isometric head shapes have a larger sweet spot ... And actually, whether the sweet spot is larger or not depends on how you transform it into a circle. If you do it by making the head wider (without changing the length of the head), then your sweet spot will increase in size. If you make it a circle by decreasing the length, then the sweet spot will be smaller.
Oh right, I meant to write that isometric heads have even larger sweet spots than oval heads. I was under the assumption that the size of the surface area stays the same, then you will have a smaller sweet spot compared to real badminton rackets.
The sweet spot is where the longest vertical strings coincide with the longest horizontal strings (approximately).