I hope I'm asking this question in the right place

After attempting to take a number of panoramic shots on various holidays, only to be disappointed when trying to stitch them together in PS CS2, I've spent the weekend looking into why things weren't working out. It seems that it's parallax error that's causing me problems. A number of sites I've seen recommend Nodal Ninja and from reviews I've read I'm keen on purchasing one, but have a couple of queries that searching hasn't answered. Hope you don't mind me asking here.

I'm using a Canon 400D body and wonder if the NN3 works with the Canon 25-105 L F4 lens and the Sigma 18-200 lens. I ask as I've read some reviews/comments stating that there is a maximum weight limit and heavy glass or the higher focal lengths can cause issues. Would that be the case for these lenses?

Also, if the planets one day align, I'm hoping to get a 5D body. Would the 24-105 still be OK with the 5D body on the NN3?

The NN5, despite being better is really out of my price range for the moment.