In the image (PDF) you posted, is each "table" from the same windowed region (same rows and columns) of the spreadsheet? Is the issue that stuff is getting left out (cut off), or is the issue that the width and/or height is different?
Each table shown in the PDF is the same windowed version.
The problem is, on the Rgiht side edge of each table. Notice that not all the edges line up. Each table is a copy of one another however different files.
"Notice that not all the edges line up."
It's still not clear to me exactly what the issue is, but in regards to this and your original question:
"How do you control the size of OLE objects created in Excel?"
I can offer you these suggestions:
1. Make sure your row heights and column widths are indeed the same within the different regions of the spreadsheet(s).
2. Make sure your zoom level is the same when copying from multiple spreadsheets.
3. When pasting multiple times from Excel into an AutoCAD DWG, do not zoom in or out between pastes. (Panning might not be a good idea either.) I don't know the exact mechanism, but in my experience (copying ranges of cells from Excel, using Paste Special as Picture into AutoCAD) the sizes tend to change if I zoom (and/or pan), but it's not consistent.
4. If a particular paste comes in with a size that doesn't match up (but should) with a previous paste, after pasting the new object use Properties to note the height or width property of the first one, and then use properties to change that property of the new one to match. (Be sure that you leave the "Lock aspect" property set to Yes.)
5. You may find that a paste comes in distorted in both dimensions, in which case you can change the "Lock aspect" property to No and then you will be able to adjust both the Height and Width to match the size of other pastes.