I went and did some estimate ID's on my pipes and found some information out (didn't have a micrometer with me at the time). I calculated my drilled out adam drake pipe at a hair under 6 mm ID so about 5.8-5.9mm and that is after all of my drilling. Stock it was probably a little under 5 mm. I did not have my sirio pipe with me at the time because it is at my friends house because he tried running it on his savage last year. I will get it a little later today and let you know. I did however measure the ID of my ofna 086 pipe and it measured in at exactly 8mm. I also measured the ID of my adam drake header and it is about 7/16 to 15/32 so I too would need the ID of my stinger to be in the 7 mm range so I am going to test it out the way it is with my drake pipe. If I am unhappy with the perfmormance of that, I will throw on my sirio pipe and see if it is any better (much larger ID stinger). Then if I am happy with how the sirio performs, I will cut off the stinger on my drake pipe and drill it out to 7 mm or larger and weld on a stinger with an ID of 7mm or larger. I should be satisfied my this point. I will let you know how it all goes. Thanks