Cannondale MT2000 set up for off road. Big beefy disc brakes, Boxer triple crown forks, Heavy duty wheels, that also are very heavy, Rear seat post rack and a few tools. and bars etc up to freeride or downhill quality.If I could come anywhere the manufacturers weight with that lot, I would be worried.

Most of you would Buy a bike and look at improving the quality of parts fitted as they require changing, and also look to lose weight at the same time. Hence My solo Bianchi that initially weighed 28lbs, now weighs 24lbs, and will still take the punishment that I dish out to it, Just a change of wheels, tyres, fork and a few Lighter weight items like bars and seatpost.
I looked at the Tandem and thought if I lightened this up, It would break, So I now have an MT2000 that weighs in excess of 50lbs, but can take any offroad that I throw at it, and will not fall apart when it does an endo. (Haven't quite done that yet, but it has taken a few tumbles with the only damage to the paintwork and the pilots pride)

On top of that, with the two riders in excess of 350lbs, why should we worry about a few lbs here and there?