Hi Terry,
I`ve used the ministeam engine in two small paddlewheelers - "Rigi" lenght 82 cm, and "Hjeilen" of about the same dimensions (both Billing Boat Kits of the sixties).
The small engine is very compact and of light weight. With the gear reduction of 1 : 11 she is surprisingly powerful, the speed of the boats is much faster than scale. In connection with a small flame tube boiler (diameter 50 mm, lenght 120 mm) you will get a good propulsion.
Of course througt the light an thin materials the engine seems a little bit fragile compared with the normal brass made engines, but for small models like the Louise it will be the right choice.
Thomas