This morning I did 43160 feet and back with my mavic. Certainly not a world-beating record but I learned some things about standard LiPO batteries with the mavic on this one. I know that everybody is on the high-voltage tip right now , but the standard LiPO batteries are amazing in the last 12%. I flew about 7000 feet in low-power mode at 22 miles per hour and I only used 6% battery. I'm figuring I have anywhere between 6 and 8 minutes left of flight time after I hit Landing mode with the 5200. I doubt very seriously the high-voltage battery would come close to that. I believe the saddlebag battery charges the main battery in landing mode. I don't know I just figured I'd share that with you guys. In my opinion though if the mavic was faster in landing mode the standard lipo would be superior to the high voltage batteries , but because it only does 22 or 23 miles an hour they can't make up the difference.
I think the very best battery setup could be the Multistar 4000mah LIPO and overpacked to 4.35V. The LIPO is much lighter than the the LiHV, saving more than 40grams between the 2 batteries. With the overpacking, you'll get the extra push on the top end of the battery and still have that extra on the bottom end. That would be the perfect setup for you as you fly the batteries so low. @dirtybum has had good results overpacking his Multistar lipos (I think he has Multistar).