The key point is that any filter must go over the front end, or objective, of the telescope. It is not safe to use filters at the backend, i.e. near the eyepiece.
I have a C6 and observe the sun using a full-aperture filter made from Baader Solar film. You can buy this film from a number of UK suppliers and make it into a filter that fits over the objective of your telescope. I made a suitable filter using cardboard and tape as shown in the picture below. Make sure that this fits snugly over the objective so that there is no danger of it coming off when you are looking through the scope.
Let me know if you need any more info.