Please note, all: I soaked the decals in decal SET, not SOLVENT. The decal set is just water and vinegar. I'm not sure what decal solvent is, but I know it sort of melts the decals, after they have been applied to the model, causing them to wrinkle up and finally settle down into the model contours, and after it is dry, usually they look very good. I think that soaking the decals in solvent while still on the paper backing would probably dissolve them, and result in a disaster before they could be applied to the model.
The decals I used in this experiment were aftermarket, made by a company called Zotz, in Mexico. They seem to be high quality and this technique worked fine with them. I do not know what the results would be with other brands of decals.
I would be interested to hear of any other experiences with this technique, with other brands of decals.