When you say gigastacked, do you mean that you've connected the 5 switches together via the gig ethernet ports? You can trunk either the gig or fast ethernet ports in this case. If it were me, I would trunk the gig ports. The port you're trunking of course has to actually be physically connected to another device of course (which ever port/ports are connected via ethernet or fiber) with the same encapsulation on either side, etc. As far as vlan propogation, that's simple enough. Just make sure they are all in the same VTP domain, one is set to server, and the rest are set to client (or transparent of course if you need it to retain it's own vlan information.)
