Tabs, the gutter, `window-height', scrolling. (Was: Re: OK I give up)

I imagine this must have been noticed by others, and is likely on someone's ToDo list anyway, but it can't hurt to point it out if I keep it brief... With the tabs displayed, when I push the page-down key, it doesn't put the line that was at the bottom on the top line like it used to. That line is off the top of the window now. I looked at `window-height', and see that it accounts for the modeline and possible scrollbar, but it does not (yet) account for the tab gutter, and needs to. I am not capable at this time of making that patch, or I would. I just plain don't understand things well enough yet to monkey with it.