drawing a line with an arrow head.

I want to draw a line with an arrow head on my web page.
I’ve created a WebContainer called myDiagram in which to draw this object, and I will embed it within this web container.

My question is …
should I create a new WebContainer which has a WebCanvas, call it Arrow and then draw the arrow in the WebCanvas paint event?
Must this WebCanvas be in a WebContainer or could I simply embed the WebCanvas in myDiagram?

How many of these can I practically manage on a web page? 5, 10? 100? 1000? 100000?