I don't care how freakin' small the Gundam pilots are, or how skinny Marron is, or blah, blah. Each of the characters are characters in their own right, and don't deserve to by stylized in that way. Marron may not be able to chop firewood with his hands, but he's not weak! (Look a manga volume 6 for the coolest swordsman ever.) In and out of bed, most of your characters, unless they are injured, disabled, or, through cannon characterization weak, can perform capable. This is the same with how I feel about Duo's perpetually "pale" skin. All these fic authors describe Duo as this pale little boy, like Marron or something. Take a look at the pictures from the show. he's really not that freakin' pale! He's, like, a shade lighter than Heero! ::Rolls her eyes.::
Secondly, don't go telling me that any one character is one-dimensional. Marron, no matter how sweet he is, has some idea of what two men do when they have sex. I'm sorry, but this weeping-uke mentality (mostly born of "weeping-uke" doujinshi and yaoi manga) is not appealing. I don't know who would want to make their boyfriend (or girlfriend) cry when they slept together, but come on! Unless we're talking about something that is very traumatic, or unless Marron's crying those illusive (to non-fictional people) tears of joy, no one should be crying! If you are crying during sex, you're prooobably not ready for it. Carrot is not such a jerk that he wouldn't, like, kill Marron over wanting to sleep with Gateau. He might not like it, but don't buy into stupid sterotypes and turn Carrot into a detestable, one-sided biggot.
Lastly... Be realistic! Kaeru's right! You're probably not going to enjoy your boyfriend's jizz. It's kind of like saying, "I just drank my boyfriend's blood, and, boy, did it ever taste nummy!" Unless your Lestat, that ain't gonna cut it. Nor is it cool to claim that giving someone a blowjob is going to get you off. (Sorry to be so crude.) It's been said a lot, but I'm gonna say it again. It's not terribly likely that giving someone oral sex is going to make you have an orgasm. Them? Sure, that happens all the time. But giving pleasure doesn't always mean receiving it, as in cases like this.
And, as a public service announcement, I'd like to let everyone know that sex isn't always perfect. There's no possible way that having sex with someone is going to be as flawless as fic authors would like you to believe.