There are probably many bi guys in straight porn, but the problem is that after doing gay porn, the majority of the straight females will not work with a bi porn actor. This is not the case in Slovakia or the Czech Republic, but they have different mores. Frank Tower found that doing gay porn was a real career killer and several other actors have encountered the same fate. I hope the handsome Kurt Lockwood doesn't suffer the same fate. From talking to "straight" guys who have done double penetration on a woman, it is VERY homoerotic, so it doesn't seem a stretch to me to think that many of the straight porn actors who would do a double vaginal or anal penetrations scene would very likely cross the fence when the cameras weren't rolling.
BTW, one of the hottest homoerotic straight porn scenes was with 2 German dudes fucking a woman who blew them both and then proceeded to kiss both of them with both of their cum on her lips and face. They acted like they didn't like it....but you never know