How Should I Ask My Friend To Masturbate With Me?

I'm almost 14 and I'm a Bisexual male, and I've known this for over a year now. I figured out that I was Bisexual by, first off, the locker rooms in 7th grade. I also have had crushes on three guys in my school, so I think it's a very safe bet that I am sexually and romantically attracted to guys. I also know that I like girls, but I like guys a lot more. I'm just more comfortable and connected with guys. I came out to my friends at school about a year ago, and I came out to my best friend (who is also almost 14) about three months later (it only took so long because he lives in a different town than I). He is very alright with it. In fact, he is okay with talking about how he masturbates, watches porn, and sexual experiences he's had with girls to me. Not only that, but whenever we have a sleepover, he is unafraid to get half naked in front of me when he gets ready for bed. We also watch porn together. I even asked him, and he said that a lot of people are Gay and Bisexual, and that he doesn't mind. Now, I'm not saying that he wants to have sex with me; I'm just saying that he's comfortable with me. Anyways, I was thinking of masturbating with him on our next sleepover (which is only a few days away), and I was wondering on how I should ask him. I was thinking we should put on some porn, as we usually do on our sleepovers, and see how things go from there. I don't plan on getting into a relationship with him, I just want to experiment with him. I've read that, according to the Hite Report on Male Sexuality, 43% of guys have masturbated in full view of another guy as teens. I've also heard that the guys who masturbated with a friend as a teenager are still friends with these people, and that in most of the cases they are both straight. Not only that, but since he is so comfortable with me, I don't think that he will view us masturbating together as something with a lot of meaning; he'll probably just view it as something boys do at sleepovers. I know what a lot of you people will think, but trust me, I've known him for over 11 years, and I doubt that this'll ruin us. But, I don't want him to feel uncomfortable with me, so can you guys give me some advice on what and what not to do? Do you guys think that my idea of just watching porn with him and seeing how things go from there is good? Please, let me know. I appreciate your help.