To the best of my knowledge, It shouldn't be a problem since the fuselage kit has not been started. It will require trashing some ribs and at least the forward top skin and buying the required tip-up parts from vans. I don't know about the rear top skin since I am not there yet. Just call Vans and they can tell what you will need out of the fuselage kit to make the change. Once you have the new parts, you can just follow the plans for the tip-up.
Jim Kinsey
7A Fuselage almost tipped