Cat 323f with thumb and jackhammer?

I am looking to rent a 323f excavator with a thumb to dig some trees and remove a rock as well. The problem is that there is a large rock that I will need to use a jack hammer on but I also need the thumb for tree removal. Dealer says that you cant run a jackhammer with the thumb on. So I was wondering if any one has ever ran a excavator with a thumb and jackhammer or if it is possible? I don't understand why cant just fold the thumb up and unhook the hoses and run the jack hammer. Is there something that I am missing?
thanks

I think the dealer thought that you are trying to run both at same time. I don't see why you can't fold the thumb up and switch the hoses to run the hammer.

Depends where the thumb pin is. On bucket or on stick.

I have a 324E with a hyd thumb, the aux circuit has a t in it for the thumb and two sets of valves, when I want to hammer I just roll the thumb up, close the valves to it, hook the breaker up and open the valves to it. It works good but you have to take the clamps off of the breaker that hold the hoses otherwise when you roll it in they hit the thumb and bend/break bolts. Just have to be careful and watch the hoses.