Rocketeer:
I think I understand your 2nd puzzle and final clue - BUT frustratingly haven't succeeded yet.
Please kindly verify that all of your rice "recipies" are accurate (unless my suspicion that 1, 2, & 4 are the variables is not correct...)?
Thanx for the game!!!! 
Oops, you are correct Rocketeer. Thanks for the clarification. Fixed now. The recipe is inaccurate, but the puzzle was correct. Your variables are correct too, just not in the right position (my fault). Anyway, checked it through thoroughly, it should work now. Sorry for any inconvenience caused.
Oh, and do remember, that since it's a list, you should add not multiply.
And lastly, remember about the not negative or positive clue. Once you have 7 numbers, you may need to guess a little about where the placement of the final number should be. Try every combination (there shouldn't be too many, if you have the 8 numbers correct).
P.S. Since Volvo did this, I'll do this too.
Puzzle 4- China
Puzzle 8- Revealed 1st July
Puzzle 12- Revealed 10th July
Puzzle 16- Revealed 20th July
Puzzle 20- Revealed 30th July
If you can't solve the puzzles, maybe you can speculate on the route you're taking, gives you a hint on the coordinates...