This would be in the eye of the beholder I'm thinking.
In mine it would be crossdressing if you are wearing any clothing of the opposite sex. Whether that is just a pair of heels or the complete look it would qualify as crossdressing. I've spoken to many over the years and found the range from those that fixate on a particular article of clothing to those of us who emulate a woman completely and I believe we are all crossdressing. The exception to this of course would be those sisters who are transsexual.
My humble opinion...and yes, it's only worth 2 cents in this economy...