I was shooting this weekend and ran into some issues when assembling the images. I am not sure why this is happening but my final image looks squished and distorted at the top. I realize there are some distortions to deal with when shooting a panoramic but I am trying to minimize this.

I was shooting a 17mm-85mm Canon lens 180 degrees in the horizontal 10 images, 4 rows in vertical (-30, 0, 30, 60 degrees) for a mosaic image of 40 images.

Any ideas on how to minimizes this? I was thinking to increase the amount of images shot by using a lens that is not as wide as 17mm, maybe a 50mm.