I have a Wilson k factor six 90 and another k factor, the k88; they are both the same grip size, 3/8. I had used them for a while and they were fine but when i started playing against a better opponent than me i noticed that all of a sudden the grip felt too thick and it was messing up my game. I guess it was because i had to respond faster as opposed to when i played with weaker opponents, where i had more time. Either way i started noticing that the grip felt thick anyways and didn't allow me that much wrist action in the serve and well basically on all the other strokes. So what i did was remove the original leather grip they came with and put 2 regular overgrips instead. They were lighter and the handle was thinner but they feel off in some way. They feel like off-center and unbalanced, i don't know how to explain it. I have another k88 but this one is 1/4 grip size so it feels really good. It may be that my real grip size is 1/4. I haven't removed the original leather grip on this 1/4 of course so it feels solid and better than the other 2. So could it be that taking off the original leather grip and putting 2 regular ones, which are thinner and lighter, messed up something?