CK also uses a linear accelerator, it's just a miniature one that's mounted on its robotic arm. "Linear accelerator" (or LINAC) usually implies the full-size version though, usually with the 5-week FSR protocol.
There was a lady on here a year or so ago that was refused or discouraged from CK treatment in Minn. I'm not sure if it was because of the size, her age, or something else. Anyway, she ended up going to Stanford for CK and is doing fine as far as I know. Her screen name is Anomar11 (real name Mona). She might respond to a PM or you could find some of her posts with the Search function.
I put some pics up awhile back of what swelling looks like on MRI. You can see here
http://anausa.org/forum/index.php?topic=7234.0 if you like. It sounds like yours is about the size of mine at 4-7 months post-CK (middle pics in link), when I had the most swelling. Most people don't have that much swelling, but you can see how it pushes things around inside your head if it does happen.
Not sure if more fractions would mean less swelling or not. It doesn't seem unreasonable (in my non-expert opinion), but probably almost impossible to prove with all the other variables involved.
It's a tough decision. I wish you well.
JB