You can...unbolt it, drill 4 new holes farther back, and re-attach in the 4 new holes. Just make sure the spoiler still covers up the old holes or fill them in.
This may sound stupid, but measure twice, drill once.
This was one of the best visual mods I've done to my car. Only Mustang guys know what you did, but the difference is amazing.
I started to do mine but when I removed my spoiler I found dirt had embeded itself into the clearcoat and I couldn't handle it looking so chity.. I plan on removing the wing again and having the trunk lid buffed out and then I will move mine back..