[thierry_st_malo]

Thank you for the compliment :-)
About your question, most of these boats were designed for riverine operations only. So, they had as reduced a draught as possible, their hull was only as deep as was required to house their boilers and engines, and a high freeboard was not required; so it was kept to a minimum to reduce hull weight, and thereby draught. Also, a reduced freeboard made the boats smaller targets. In most cases the hull section was practically rectangular.