I've been bowhunting for nearly 40 years, used many different broadheads and bow combinations. I would not even consider using any mechanical head with anything less than 60#. 40# would definitely be out of the question.
There are many COC and replaceable blade heads that will get the job done Something with a narrow cut and no more than 3 blades would be my recommendation. And tune till arrow flight is as perfect as you can get it.