The staff at Voltz Toys have amazing customer service and are prompt to respond when you have questions.
My son loved the Unimog. It fits 2 smaller children 4 and under comfortably and is powerful enough to drive through a grass field. The remote is quite sensitive so you have to make sure to tap the left/right buttons as apposed to holding them down.

I do agree that the instruction manual isn't the greatest so here are a couple of tips that aren't in the manual.
1. There are additional tools required to make the job easier include a #17 socket wrench, stronger screws for the seatbelt and a rubber mallet.
2. The lap part of the seatbelt needs to be screwed into the support bar under the seat. YOU MUST PUT A SCREW w' WASHER THROUGH THE SEAT BELT STRAP. I used a more heavy duty screw to make sure the lap seat belt strap was secure.
3. The bottom half of the seat doesn't line up with the screw holes unless you apply a lot of pressure and push the seat back as far as you can.
4. Use a rubber mallet to gently hammer the rear plastic frame into the main body of the Unimog.
5. The remote is shaped a bit funny and it feels like you're holding it upside down. Make sure it's oriented properly and if you want to quick stop the car remotely press the "p" button.

PRO
- battery is awesome ( can pull two kids easily up hills)
- last very long ( have driven it over an hour ... no problem)
- love the remote control feature ( feels secure especially when you have a kid driving)
- good space for two big kids

CONS
- seat belt is useless
- the back handle needs more screws to keep in place
- noisy mechanism ( i think it's the motors )