Yup, RIR roo can be very mean. My grandpa had a RIR roo that you could never turn your back to if you were in the coop collecting eggs. I was attacked by him several time as a little kid. I still have a scar on the back of my leg from an attack 30 years ago. Left some bad lifelong impressions on me.
I kept on raising RIR and hatching them, but the roos all end up in the pot. I just got rid of a RIR roo who was about 5 months old and he started puffing up and making threating advances toward me and my kids when we go in the coop. He made a really good pot of chicken papaya soup.
Right now I have a austrolorp and barred rock roo that are both so tame that my 3 year old daughter carries them around. Its going to break my heart when I have to tell her either Keoki or Rocky is going to have to go for a permanant visit to her uncles house (she doesn't know about the pot yet) because I only keep 1 roo for my girls.
If you aren't 100% stuck on hatching and selling RIR, give barred rocks a thought. They are what most people remember as grandmas chickens. Very popular backyard bird a couple generations ago. They lay large light brown eggs and are very gentle a docile, even the roos.
Best of luck with your project.
Aloha,
Cory