Hmmm.
I tried the dynomat trunk kit, I ended up paying like 135 for it.It does it job no doubt , but kinda pricey.I did a little research for other products, many of them cheaper then dynomat.Anywho, what I ended up trying was Ice and water shield, which is normally used on roof's to protect against the elements.I work for a masonry company that mostly work on new homes, so i find this stuff everywhere.In two weeks i ve got enough to do my car twice.But if i had to buy it, it would be about 100$ for 75 sq feet.
Hopefully this helps u out, dynomats expensive.Dont get me wrong, ice and water shield aint equivalent.But does the trick for me..Maybe one of your friends works construction or something..
Good luck