Hmm... would you happen to be using retail? Because I tried that method recently on my steam version, and after i added current inventory +16 manually, the memory address was MUCH bigger than the 120 it should have been. Could you explain how you found that address offset so I could look for it in my steam game?
...****... Yep, that was the problem.. i was adding +16, not +10, which does work on steam.
I would use the toolset for it, but my toolset doesnt work for some reason (i'm pretty sure its because of some random SQL error on install), but your method seems to work perfectly with no problem whatsoever (except for a few stupid errors, like me not realizing that the +16 was dec, not hex).