"twinned"servos on 1 axis

I am close to mounting 2 servos that will drive my large gantry,

I am hoping I can bench tune them before mounting
my theory is that since reflected load at 15:1 reduction should be
negligible,less than 5 in lbs, I might not have to retune once they
are mounted.
any criticism ,suggestions and warnings are appreciated
thanks
Carl