Do you have your mains and crosses strung at the same tension? As a longtime Yonex user, I have found that the opinions on the matter from users and stringers is decidedly mixed. When I used the R-50 and R-70 years ago, my stringing pro told me i should drop the tension on the crosses by five pounds because of the head shape. So I've been doing the same for the last 12 years with my RD-7s, but some of the people who have strung my racquet over the years have said Yonex doesn't recommend it.