If Solvaset does not work, use Champ decal set. I can just about ger-on-tee it will set it down. This stuff is really, really, agressive. I usually put a small amount on a brush tip, hit the decal in the area to go down, then follow with a water damp tissue to stop the action after a few seconds. Wait a little bit, if it hasn't set down, it should be soft enough to just push it down with a brush that is just moistened with water. If it' really stuborn and still lifts, keep working it with the brush. It will stay down after a couple of tries. Let it sit for minimum 24 hours, any wrinkling should go away. Then overcoat with your favoirte clear coat. I would wait a week if overcoating with Future.
Champ is a railroad decal setting solution, and can be hard to find. But, a bottle lasts forever.