It seems that once embedded to a blog, scenes tend to go missing. So, in the hopes that by not making them viewable here, they remain on the sites at which I found them, I'll just post links to them here.
I found this one a few days ago, and I'd love to find more of it. I'll continue to search from time to time, but for now, this shot clip at 'daily motion' is pretty hot. Though short, and ending at just the point that it reaches one of my favorite types of scenario, This M to F Transformation deserves a look. If anyone happens to know the title of this movie, there are sure to be those who'd like to know it... as would I! The channel of the user who posted this brief clip has many, many TG / TF clips.
A couple of scenes from a XXX version of the classic Dr. J. & Mr. H.star one of my favorite ladies of the adult film industry as the good Dr. post-transformation(s?) engaging in 'straight' sex, (if you ignore the concept that the woman was a man before imbibing whatever compound induced his change into a gorgeous, libidinous woman) This scene contains reference to the fact that he is now a woman. While this one is, I believe, the Dr's. attempt to collect some male 'material' in order to reverse his female state; (with the scenes of context not being posted, as far as my searches have found, it is hard to tell.)
Here is the 3-X opposite of the above, in which a F to M morph of the kinky Dr. , for purposes of being a complete 'switch-hitter', reverses after an extended session of 'straight' sex. But, she's not done.
As the TG / TF segment is not very popular, it seems, at the tubes sites which have lengthy sex scenes, the contextual portions are sadly not so prevalent as the intercourse that results. Thus, keeping in mind that the protagonist has been transformed is helpful. It may be that in time, and with enough request for doing so, the transformation / contextual scenes might be posted.
I hope you enjoy this selection. Also, I have found more and will post some links to them at some point in the future.