Oh your planning to drag race with it, makes sense now.
I have no idea about drag racing at all. A lot of local guys are into it and I believe they contact Steve neu and have him make custom motors for them.
Your logic makes sense about running the lower kv motors on 6s.
Id contact neu and see if he has a better option.
Until you pointed it out I had no idea that the max motor length on the cobra is 68mm, your right people barely fit the 4030 buggy motors(71mm) in the cobra be. I was hoping to use a 2250 4038 truggy motor but it's 5mm longer then the buggy motor so there no way it's going to fit. I guess my only 2 options are the 4030 2050 or the 2650. I have a tekin 2650 but it's a little bit over kill on the track plus motor temps are so much better with the 2250 truggy motor. Maybe I'll order a 2050 motor and see how that does