Wanted to add to the comments made sofar that i had better results using handwarm water as opposed to straight from the tap. Used cold the decals sometimes needed a full minute (!) of soaking before they started to slide off.
Using warm water it was more like 20 seconds.
Also found that after applying the decals the normal way (i.e. set, soak, apply, dry and sol), it would definately help to puncture the decal very carefully at some places and give it another (few) coats of sol. This worked especially for the bigger decals.
You can use the academy decals and get good results, they just need more work
Richard