[CS4] Custom PageItem creating

I want to create a line pageitem not using PathUtils.

In brief:

I created a command kNewPageItemCmdBoss and set up  INewPageItemCmdData for it:

createCommandData->Set(database, kMyOwnNewPageItemBoss, INewPageItemCmdData::kDefaultGraphicAttributes, parentUID, linePMPointList);

linePMPointList  defined, for example, as follows:

PMPointList listPoints;
            listPoints.push_back(PMPoint());
            listPoints.push_back(PMPoint(PMReal(150.0), PMReal(300.0)));

in *.fr
Class
{

     kMyOwnNewPageItemBoss,
     kSplineItemBoss,
    {
    }
}

As a result I get an object without width and height (point-like, invisible, but selectable) with the properly UID.

Question: Where and what to add that as a result to get the line?
There are several methods in the PathUtils (like CreateLineSpline, CreateOvalSpline, etc.), but all the difference is in the name of a method...

Most important is to create a line with a boss inherited from kSplineItemBoss, but CreateLineSpline method of  PathUtils does not allow a specific class except kSplineItemBoss...

Thanks a lot for help  in advance,
Viacheslav