Iv been yoyoing for a while now and hav always positioned the slipkot far back on my middle finger does this make a lot of difference because I know it is usually positioned between your first and second knuckle
i keep it 75% to the tip
It doesnt really change much except mounts may look different or be harder to hit. I used to do that too, but i changed and found i liked it better.
i put it far back on my middle finger
As far as I can imagine, the only way it can be bad is that you can’t loop with the slipknot far back.
It makes no difference as long as it is comfortable on your finger. I put it right on my first knuckle and maybe when I want to mess around I’ll put it right on the tip of my finger 
Actually it does make a difference. I have put the slipnot in every position you could think of. When it’s at the base of your finger certain mounts are very hard to hit. You loose a lot of contro;. Being able to move that string a few inches makes it possible to get into a mount where the strings are very close. Moving that string out of the way is necessary to get into that position. Without being able to move that string you just limited yourself.
I keep it on the first knuckle, nearest the tip. Gives more control there.