How do you come up with 11MB per chapter? A lot of older readers have a limit of 300kb per xhtml file (uncompressed), but that is not including images.
I am sure that readers have limits with regards to size of an image due to memory, but I haven't reached it yet. The number of images should not be a problem.
Besides the overal size, there should not be a problem to have 161 images. Just keep your chapters small.