The single piece of info is what container size is she buying. (ie NJ, OJK, TJN etc..)
Once you know that you can go to the manufacture's site and find out their recommended sizes. If the rig is tight with a 150 in there, a 170 is probably a bad idea. Best thing is to talk to your rigger with these details. For example, I have a Javelin Odyssey OJK, and I have a 135 in there, but there has been a 150 in there. I'd only recommend doing this if your rigger gives you the go-ahead.
Edit: Even better, talk to the manufacture, tell them what you plan on doing and if you're buying a rig, they're usually more than happy to assist.
(This post was edited by Chris-Ottawa on Jul 19, 2006, 2:57 PM)