Brushless 1/8 Buggy

[Batfish]

I have a new question:
If I'm planning on running on possibly 6 to 8 cells, should I use a different motor? 9L? 8L?
I have read a few posts from someone tracking their 1/8 buggy at 28MPH with a single 6-cell stick pack using a 9918 and 9L geared the same way I'll be gearing. What I'd like to do is run two packs in parallel to increase runtime while being able to run ~30MPH, so I'm figuring 14 or 16 cells, but wired as one 7 or 8 cell pack.
The buggy is listed at 7.7lbs before removing the exhaust pipe and brakes, and adding electronics and batteries. I figure up to 2.2lbs of batteries, plus the weight of the receiver, servo, speed control, and motor. About 11-12lbs RTR?
I just want to make sure I'm getting the right motor for my application.

Again, my goal is to have a brushless 1/8 buggy that can run near 30MPH for ~15 minutes. Ideally, the motor and speed control would be able to handle that twice; back-to-back, so ~30 min at about 30MPH. Right now it looks like the 9918 for sure, just looking for the advice on the right motor.

Thank you.