I've been able to slide most servo frames under and into the servo opening even when the frame is bigger than the opening. This is in fact normal for most of the servo frames I've used.
High quality servo frames that work great. Makes for easier servo replacement, and bearing mounted trays greatly reduce play in the servo for better centering and
alofthobbies.com
While Futaba seems to have a good reputation. They are the brand of servo I've had the worst experience with. Now this was 30 to 40 years ago. OK, Blue Arrow were worse.
Today as everybody sources the same electronics I think servo performance comes down to gear trains and software. As to spec's I hope you aren't spec'ing the servo so close as to not have head room for marketing hype, over speed and under voltage.
I love my MKS servos and my KST servos.
MKS-HV6110 Mini Servo
alofthobbies.com
I also like my KS servo and Power HD servos it all depends on the application. But it is true no KS servo can compare to a KST servo on their own merits. The KS servo has too much backlash. But for the price of one KST I can supply a whole ship set of KS servos. This is why I use 100% to 120% of the servo motion, resolution and backlash issues are minimized.
I shake my head in disbelief when I see radio programs with the servo limited to 70% motion!