How can I add more contour lines to a wireframe chart?

How can I add more contour lines to a wireframe chart? The contour plot that Excel created automatically only has two contour lines. The maximum of the Z-axis is about 2500 so I want to have contour lines for Z equals: 0, 500, 1000, 1500, and 2000.

Is there a way to specify the contours?
Excel 2016
Attachment 29166Attachment 29167

Can you attach a workbook so we can 'play'?

1) I found how to set the contour lines by setting axis-z gridlines. It is hard to get to the settings.

Select chart area (chart elements [+] shows sometimes, ignored
r-click [format floor]
[floor options menu], select [vertical (value) axis]
select [axis options menu], select histogram icon=axis options
Bounds
minimum
maximum
Units
Major = this is the contour interval

2) I tried switching rows and columns in the "select data" window. That would probably be my favorite approach if I could size the plot area independently of the chart area -- because it is so small. I can't find how to move the plot area within the chart area.

3) I tried to reduce the number of categories by selecting only rows 7-30 plus row 2 for the H-axis. That works but the plot area is half as wide as chart area.

4) I tried to make contours to be all dark black with ability to label them with axis-z value (500, 1000, 1500, 2000, 2500). Couldn't make this work.

Attachment 29169

Is this what you're after?:
Attachment 29172

Thanks. How did you control the size of the plot area -- which is sometimes for me way smaller than the chart area.

I didn't make any real efforts to do that, that's just how it came out.