The allowable dimensions of the Falkirk Wheel is as follows:

Length 70' 0" 21.33m Beam 19' 8" 6.0m

Headroom 9' 0" 2.74m

Draught 4' 6" 1.37m

The caissons can hold 300 tonnes of water so I guess the maximum weight of a craft would be around 200 tonnes

A craft carrying commercial freight has done the journey from Edinburgh to Glasgow this week (03-07-2003) carrying 200 tones of aggregate - the first commercial freight on the Forth & Clyde and the Union canals for over 70 years.