Try soaking in water overnight. water will eventually soften and weaken it. Do not use suprglue for windows, you are asking for trouble. Try a good PVA glue like Formula 560 Canopy Glue or Microscale Krystal Klear. It can be rubbed right off or wiped off with water on a Q-Tip. It does take awhile to setup but the safety factor is worth it. It holds very well when dry.
This one was finished about 2 months ago but I just now took some pictures. The work in progress is here http://www.modelcarsmag.com/forums/topic/100895-mclaren-f1-gtr-update-decals-51915/#comment-1410302
It is a great kit but beware anybody buying Tamiya kits from this time period(early to mid nineties) Tamiya had issues with cracking decals. I would not buy these kits unless I could see the decals in person.
This stuff is primer only in name. None of of it is a proper primer. This becomes evident when sanding. It does not sand and feather edge like a true primer like Plastikote,Duplicolor or Tamiya. It's really just gray paint.
Looking good JC. I always buy enough paint intending on sanding the firs coats down, The second session always comes out better. I learned that in wood shop in high school. The more coats sanded in between the smoother it gets. The reason is most primers are porous and soak up the first layers of paint, color coats seal the primer and you get smoother paint.