However, you could consider shrinking your main partition using gparted live. Then put a new /boot at the end. Of course, you'd lose the original /boot partition space, however.
1. Shrink the main partition 2. Move the main partition to the right, leaving free space between it and /boot 3. Resize /boot to fit into the newly freed space
That's what I did at one point to make my /boot 2gb or so, haven't had issues since.
The whole filesystem has to be moved, instead of just the excess data.
Although this is usually successful, my advice would be: don't have a power outage if you're moving the whole filesystem.