I tried this servo out about a year ago maybe even longer and it worked great as long as your steering rack had very minimal play, as soon as it wore in good and had some decent slop but not too much to worry about the servo would bind. Just my 2 pennies, id stick with a standard size servo, the spectrums that all the team guys are running work great, sorry i cant think of the number right now but very reasonable and close to the cost of that savox.
For the 1251 you just have to dremel the rack a little on the right side. It barely catches. My 1257 did the same thing.