As a former voleenteer to helped out tourny organizers, I say just put it on the proper sized base.
http://www.games-workshop.com/gws/catalog/productDetail.jsp?catId=cat470008a&prodId=prod1590002
In my experience as long as you do this, then their should no no problems and less sticking points for argument. As long as it's on the proper base for that unit, and looks correct on that base it should be fine.
Another rule of thumb for stuff like this. It's always better to step up in base size, then use a smaller one. Generally speaking larger bases are a disadvantage in
40k. (That's why you get silliness like people trying to use old school metal termies that use the smaller 25mm bases.) It's annoying how many people did that in the hay-day of 5th's tourney scene....
So I'd say you could even use the 60mm base that comes with the wraithlord just fine since it's ever so slightly larger then the large flying stand. In all honesty alot of people will glue the flight stand base ontop of a 60mm base to make it easier to base the model to match the rest of their army.