Steel has an SG of ~7.8 , Titanium 4.5 ........ perhaps allowing for the air spaces between the balls, it's steel?
Info from http://www.engineeringtoolbox.com/specific-gravity-solids-metals-d_293.html
I don't know if anybody has suggested this ...... but how about a LBSC C2X?
http://www.semgonline.com/steam/c2-c2x_01.html
It would be a useful loco for small and large layouts, plus I would probably have two
Woefully off topic Iknow .... but.........
Changing the bushes in the suspension would help 'reconnect' to the steering and generally checking as Derek said for blocked vents. Yes headlights can seem a little narrow in their reach ... get some contemporary driving lamps perhaps? My Mini has 4 Cibies in addition to H4 lamp upgrade
Not nice, my sympathy and understanding, Sir. I once spent an entire week's holiday in the home we were staying in with a throbbing tooth, never ventured out once.
If you're worried about the stability, you could use water filled 5 litre cans on bearers on the leg stretchers.
You carry them empty and fill up at the venue, thus they're really light to move.