Mongo needs lens help please

[mongo]

Need help to choose a good all round walkabout lens for trip to Europe – Nikon system.

Mongo is thinking 18-200 VR OR 24-120VR assuming Mongo will have an FX camera body also by then.

Here is the problem you can help with . If anyone has an 18-200 Nikkor and an FX body, can you please tell him if it is possible to use the two together and if so, what is the widest you can get the 18-200 on the FX without distorting or vignetting too much , that is, what is the widest that lens can be really and happily used on that camera body ??

It has been Mongo’s experience that DX lenses on full frame do work quite well to a point e.g. his 11-18mm Tokina works OK on full frame film camera at about 14mm upward. Mongo is hoping that the 18-200 may work well enough at say, 22 to 24 mm wide – if it does, its his pick.

Anyone that can help with a real and practical confirmation (rather than theoretical) of the above exercise would by much thanked by Mongo

Mongo is working right now but will check any answers tonight when he gets back to his cave

thanks