If you soaked the seal with silicone spray and it still squeaks you
are not lubing the right parts. If you are sure it is seal, soak
behind the seals as well. (It may not be seals at all though)
-----------------
The SnoMan
www.thesnoman.com

If the doors are properly aligned as you say then the seal has dried out
producing the squeak at speed and on bumpy roads. I use a simple solution.

Try some vaseline petroleum jelly. Apply it sparingly, just enough to
darken the seal without leaving and sticky "residue". The seal will
become somewhat sticky until the seal absorbs the vaseline. Usually
severall applications are required. Do it during the day when the
daytime heat will make the vaseline especially viscous.

Another solution, albeit more costly, is to replace the seal. This will
always work as long as the seal is the problem. JC Whitney has a pretty
complete line of seal products if you don't want to get soaked at a Ford
 dealership.

Good luck!