Hello,

.jar files are just zip files, so you can unzip ubooquity.jar and edit the file ./comicreader/comicreader.js , search for IMAGE_MAX_NATIV_WIDTH and put the value of your choice (I go with 3000) then re-zip the whole folder as a new "ubooquity-modified.jar" (for instance) and run that one.

Doing this again at each update is a bit of hassle - although Ubooquity updates aren't that frequent :-) 

And here we are with a new release : don't forget to update your comicreader.js, folks ! ;)