I have some packages with large res images. I was wondering what the best way was to speed it up.

Basically when scrolling on the page or switching pages it is pretty slow. Lower res images seem quicker. Some of the packages are high res images are in rar. i'm not sure if it's faster with other formats.

Convert the file within ComicRack to .cbz or unpack it manually and repack it using the option to "Store" to files.
It's called Store in WinRar, other programs may call it something else.
Basically just go for as low compression as you can, or none at all if possible.
The less compression there is, the less time is needed to access and work with the file, but the larger the file of course.

.cbr I find to be slower than .cbz just due to the higher compression