The pinchs I've been getting vary from about 3mm slits to 7mm. Sometimes they're close enough together that I'm able to use one big one and that'll hold it or I'll use two of the really small ones. And I've been fixing them, I've used three different inner tubes in the last week and five days but one was an old one because I keep punctured ones in case a valve brakes and I really need one.
I'll look at the rim, it is ground but it's pretty worn out now. Hopefully that'll help. I also bought a Maxxis DH tube and again, hopefully that'll help.
Thanks for all the replys