I dont see how he could really- both servos are on steering duty , so a 3rd mini servo would have to be custom mounted to the rx box or something.
On the steering servo front (this is like watching my own build in many respects- even the thread title is a ripoff
), the hs645mgs arent really all that high torque, so you really do have to run a pair of them in a maxx (150in/oz each or there abouts)- they wont turn my jumbomaxx rubber at at standstill, but with more sensible tires I think they'll do just fine.
Funny, for a minute there I thought you were the guy who bought my modified motor mount I made a year or so ago...