I have not shot huge numbers of Sika, about 20 over the past three or four years, plus I have witnessed about another 10-12 shot by a friend of mine.
My observation is that if shot placement is less than perfect, expect a runner, big time. It has only happened to me once, but the hind made about 600 yards.
Even with perfect placement, ie top of the heart and bottom of the lungs shredded, stag's in particular can make 80-100m into the thickest wettest hole they can find. Sika are noticeably harder to put down tha similar sized fallow.
On the other hand, quite a few have dropped on the spot instantly to the shot.
My view, reinforced by some much more experienced guys, is that you really want velocity on Sika: 120's in 6.5, 130's in 270. Some guys use the 110 V-max in the 270 pushed as hard as possible. Hit 'em hard and hope for the best.