There is an old yarn, and if I offend anyone then please accept my apologies in advance.
But TS's are for straight males and drag queens are for gay ones.
So having a masculine desire, or a curiosity, for what might happen if you're with a transsexual seems very normal to me.
If I were a guy, I'd wish to try everything. Guess that in a few ways, I feel that way as a female. gulp.
I appreciate you starting this topic. You're not alone in your curiosity (don't listen to the naysayers, in Another Realm, that's just ridiculous) and I feel that a few brave guys might even send you a PM with some suggestions.
Maybe?
Best,
Elisabeth
PS You might wish to keep in mind that in my experience, a TS IS female, at least emotionally and in her heart. Also, a TS is female in the eyes of the law in many areas of life, too. So whether or not you have a threesome, you're going to be with an additional female that just happens, in many (most?) cases, still has a penis.
Hope this helps some.