The preview pane in Chart Studio does not increase chart size.  It will only allow you to preview changes to chart size.  Resizing Vantage Charts is done in Report Studio.  Resize a Vantage Chart by following the steps below.

1. Launch the report that needs the objects resized in Report Studio. 
2. Click on the Vantage Chart place holder. 
3. On the Properties pane, click on Size and Overflow and change it to your desired size then Click OK. 
4. Click the Up arrow on the Properties pane title bar and select Conditional Block. 
5. Under the Conditional items, current block by default is set to 'Other'. This sets Report Studio properties for the image. Click on 'Size&Overflow', and set both Height and Width properties to 100%. This allows Report Studio to display the image to the full extent that it is set in the Image 'Size&Overflow' property. Click OK when done.
6. Go to Current Block and select 'Static'. This sets image properties when viewing the report in PDF. Click on 'Size&Overflow', and set both Height and Width properties to 100%. This allows the report to be displayed to the full extent that it is set in the Image 'Size&Overflow' property. Click OK when done. 
7. Go to Current Block and select 'Dynamic'. This sets image properties when viewing the report in the Report Viewer. Click on 'Size&Overflow', and set both Height and Width properties to 100%. This allows the report to be displayed to the full extent that it is set in the Image 'Size&Overflow' property. Click OK when done.
8. Click the Up arrow on the Properties pane title bar and select Block. Click on 'Size&Overflow' to set the Block size, if you want the block to be set flush against the chart then it should be set to the same size as the chart. If you want some space between the chart and the border then you should make the block slightly larger than the chart. 
9. Click on Run to verify if the dimensions set are correct, adjust chart size as necessary by following steps 2 and 3. You can adjust block size for the whitespace by repeating step 8. Once you verify the chart size, padding or spacing is to your liking, click Save.