There seems to be a plethora of HV servos coming onto the market, with most of the major brands - and even the smaller specialised ones - coming on board with a low profile offering with typical TC specs;
Standard footprint
25mm ish height
<0.10 60 deg (most well under when on 7.4v)
>7kg torque (most well over when on 7.4v!)
But how are they being powered?
I'm not aware of any top end ESCs with more than a 6V BEC, so to take advantage of the HV specs, would need either direct wiring to lipo, a dedicated RX battery (and a receiver that can handle HV) or a 7.4v external BEC
The former leaves you open to a servo that changes pace as the race goes on and voltage drops from full charge 8.4V to ~7.6V (or what ever you see after your runs) and latter two mean added weight & complexity, plus the possibility of the BEC wiggling out under acceleration and high motor current draw when voltage can drop sharply.
I use HV servos in my 5th scale with a dedicated receiver pack wired direct to them and it works really well - I barely seen 0.1-0.2V drop over a 20min run, so no performance drop off noticed.
Surely someone is using one?