honda cranks can and do break. i broke a LS crank at the fillet area next to the number2 main journal on a motor with just 300whp. i held it at 3500rpm before a launch, dropped the clutch and it went boom. it sounded like someone hit it with a sledge hammer. i didn't take any pictures of the aftermath, but my friend might still have the crank floating around his garage.
but the point of the matter is, honda did a great job overbuilding their cranks. however whenever you double, triple, or in your case more than quadruple, the power output of ANY motor, you're going to have to make sacrifices. if you maintain your opinion and use a stock crank, the sacrifice might cost you the whole sum of your build if it lets go. if you however heed the advice of the people here, and a knowledgeable honda builder in your area, the sacrifice is the price of the new crank. do yourself a favor, and add up the cost of your whole build. then add in the price of a new forged crank and ask yourself if it's worth the security it offers.
