I'm *pretty sure* that the simple answer is no, the game doesn't work like that. The game measures G-forces from a point on the track level, directly below whatever seat you happen to be sitting in. So basically no matter what track/train style, in the same situation the Gs would be the same. However, while not perfect, it is still better than what you suggested. In reality, if a sitdown coaster with a 2 G hill would become a stand-up coaster, it would still have its 2 G hill. It might
feel more intense due to altered position of the riders, but it would still be approximately 2 Gs. Any change in the positive G force would be negligible.
What it does affect is the lateral G-forces, caused by the relocation of the heartline due to altered rider position. On stand-up coasters, the rider's heartline is about a foot or three higher than on a sitdown coaster, and you will see the coasters banking, trainsitions, inversions etc. modified to suit this.
-BB