[Hobohodou]

ah, this may be of no help to you at all...

I read a lot of manga on my device, so i'm used to converting it to read on it. I can sure help you with the formatting I guess

I resize everything down to 800 pixels, first changing the color mode of the document to RGB...Most devices i've seen use 600x800pixel displays at 160 DPI/PPI
I format, and change to RGB as indexed images being resized down look terrible and have hard to read text, also my device has trouble reducing an images size, so I make sure it fits the exact dimensions of the screen

So i've always changed the image sizes that way, if you Use photoshop you can setup an action for this and run it in batches...Then it's just a case of changing them onto a canvas etc of 600x800 pixels.. (you may have a problem if you use double spreads) in which case, try rotating them maybe?)

As for saving, once all the images are done, I use "pdf presentation" in photoshop, saved as a "multi page document"
In the compression tab -> do not downsample -> compression Jpeg + Medium High...
EDIT: I noticed you mentioned a 5MB limit...most of my volumes (200 pages) average at about 32MB...so I don't know how you'd get past that...but this is definitely the best format i've found for reading...

For me..this looks awesome on my device, admittedly all of my images are black and white...

Hopefully this should give you an idea of how to format the images!
any further questions just ask, especially since I only format stuff for myself...So my advice may not be the best =O
But good luck all the same !!!

(apologies for the low quality image, but my camera ran out of battery power and this was the only image taken, to show you an example of how it looks on a device using this profile)

All credit of images goes to Kubo Tite and the fantastic Maximum 7