I personally have had success with the Hitec 81 and 85 MG servos, so I like them. Others have had mixed feelings, but would easily use them again.
However, keep in mind that the Hitec 81 or 85 servos are a not direct fit for the MLST. Meaning you will need a little bit of work to get them mounted up and runing into your MLST. Not to say they won't, or wouldn't be a nice choice.
The Hitec 81 or 85 servos have a bigger sized case, so you will need to make room on your chassis. They also have a different spline count then the stocker, so you will need another arm or saver of your choice.
When I had my MLST
, I had the CAW extended chassis which accepted the bigger Hitec 81 servo. I ended up using dual 85MG servos due to they were what was available to me at the time. Even those are slightly bigger than the 81's, so a little "massaging" was needed for my chassis.
Not sure what the spline count is for tha stocker, but if you send an email to Losi (or Horizon) or give them a call, i'm sure they should know