RE: I want to use an 11.1v pack but can't go over 6v...
Check the spec's on your receiver. My JR ar7000 spectrum receiver can handle up to 9.6 volts but the servo's can not handle this power.
I have powered my receiver and servo's with a 7.2 volt nicad pack and had no issue's but I would not use it all the time. I did this to see if the system would handle this power. I used this setup in a 120 stinger with a 50cc engine, she flew great till the motor mount broke from the motor and the motor fell off, I was able to land with out any problems, the engine was hanging by the choke cable. No more HHH engines for me, ran great, just bad metal and castings.
I use 6 volt packs with no regulator, not sure if I still need one using a 6 volt pack? I have a couple really nice JR spectrum regulators with built in fan, but not sure they are needed with 6 volts, some say yes they are needed to keep voltage level.
I have no idea if a regulator is needed, seems like more wieght and another man made thing do go bad and crash my plane. So I have these really nice regulators I just store in my parts box, I look at them sometime and think, how nice, then put them back in my parts box.
I tried selling them on ebay, I could not give them away. So must not be needed to bad, no one wanted them, I could not get .99 cents for them, with free shipping. I beleive these cost somewhere around 50-70 bucks on horizon, I can't remember what I paid but was not cheap.