VSR Cylinder Head Removal?

[3AJ12]

So I've drilled the pin with a drill press, very neat and definitely far enough (too far), but i cant get the cylinder head off.

I've tries pliers and tape (the tape slips), Allen key trick (the Allen key comes out, and when it doesn't the head wont budge). I don't have access to a drill press.

Any ideas?

Thanks