Please let me put ypur mind at rest. I too was nervous about the headframe before treatment. (of course they use something similar in surgery, just youre not awake to see it). Gk and linac, which I had, use the head frame screwed in and CK and FRS use a moulded frame as its more than one treatment, often with a mouthpiece.
It's really not that bad. Here's my experience:
I had the headframe fitted at 8am and had treatment around 5pm so on a long time. This was because I had to wait for everyone else to have their treatments before the linac machine was adapted for the last treatment of the day, ie for the head. By this time it was getting a bit sore as the injections to numb the pin sites had worn off a bit by then. They fitted it so early as the neurosurgeon who oversaw the fitting was only around at 8am.
The injections are no worse than those for dental treatment, in fact less painful as not in the mouth, they sting a bit as the lignocain goes in and sound oddly crunchy. There are 4 injections. the screwing in of the pins sounds odd, but it only feels a little tight, not painful. Then you wait around for the other measurements which involves a bubble helmet with rods to get exact measurements and the CT scan.
The actual zapping is fairly quick then the headframe is removed. This is the most painful bit. It feels like long poles are being pulled from your head, which is odd as the screws are fairly small. But its over before you know it. They then put small plasters on the pin sites. Mine bled a lot and did so for a few days afterwards. But they healed up pretty quick after that and can't see them after a couple of months.
So the headframe is bearable and I've had worse procedures! It's the after effects of the radisurgery that are the real pain, ie worsening imbalance dizziness tinnitus and hearing loss (I'm 8 months post treatment). I'd still go for SRS rather than surgery though if I have a choice!
Hope that helps,