Would like to build a steam paddle tug as my first attempt using a Westbury twin cylinder unit driving approx 6 inch diameter wheels.

If anybody can advice of a suitable plan, ideally for a commercially produced hull, I would be very grateful.

Thanks.

How big is the Westbury unit?

From the Reeves site

Twin Cylinder Engine
By Edgar T Westbury
With Stephensons Valve Gear
Directly Coupled to 5 3/4" Paddle Wheels
Described in Model Engineer Vol 113-114
Length: 10 1/2"
Height: 6 1/2"
Width: 14" (minimum)  across the paddles
Cylinder Bore: 3/4"
Cylinder Stroke: 1 1/2"

plus the boiler tank and other bits and bobs    this will require quite a reasonable hull

would love to see this if it takes off

Must apologies, totally forgot to say welcome to paddleducks.  welcome 

Thank you for your welcome and advice -- much appreciated.