Yes I've had a courses of each so I've had three jabs for Rabies and three jabs for Jap E... Hate needls too but had to be done!!
Where abouts have you travelled too? Would you say our 65L backpacks are ridiculously too big for a four month + trip?
Excellent on the vaccination series! Too many people think just getting one jab for something (when it's a series of jabs) will be enough - mainly to save money. There are real reasons these vaccinations are a series. The human immune system works at it's own speed to produce antibodies.
I can't help with the pack size issue as I've never owned a backpack. But, from all the threads I've read about pack size, a 40L would seem sufficient. Here's a blog article one of our members wrote about the subject:
Hope that helps too.