From Barstow to over by Mojave it's all flat desert. But from there to Bakersfield you've got some pretty good hills to get over. A couple of long downgrades and a pretty good pull if you run that way.
Do you know what the highest elevation is? 7000 feet is no problem 10,000 takes a lot more to make but have done it already. Just thinking it will save me lots of miles.
I'm not sure on elevations, but since it's high desert I'm sure it's nowhere near 7000 ft. Probably closer to 2500-3000 ft. And it will save some time and miles. It's not a bad route by any means, but it's not flat.