Thanks for the complement.. The short answer is, No. There should not be so much deformation that the new G2F model requires very much adjustment. The reason for the arms not being at 45 degrees, is because the objective is to fit the morph to a G2F figure. So, trying to make the morph as close to the G2F model's natural JCMs is the most conducive option.
I've just done another demonstration, this time fitting a G8F morph to a G2F figure. I went through my settings pretty thoroughly during this recording, just to make sure that I wasn't missing anything. While recording the video, it occurred to me that what you're describing is almost certainly being cause by one of these two issues.
1. Make positively sure that there aren't any unintended morphs being applied at the same time that you're applying the morph that you're converting.
2. Your rigging might need to be adjusted to the G2F shape. I show you how to do that at the five minute mark of this video.
Hope this helps..
