Putting the files in are one thing, Making 1.5 read them is another! You have to remember that you will have to modify some of the files which are encrypted! If you can decrypt the file in the first place, you might aswell replace the tif library in 2.6 with the exploit and then do an upgrade with a modified firmware!

In other words, this is a long shot, but you'd probably have more luck putting the tif exploit back into 2.6 than a browser into 1.5