If you leave it as the original size and the image is too large, the image will cause the structure to be off. To get around this, you would want to limit the size of the upload, but allow it to be larger.
In your admin/Products_Insert.php file, find this block of code:
<?php
// WA_UploadResult1 Params Start
$WA_UploadResult1_Params = array();
// WA_UploadResult1_1 Start
$WA_UploadResult1_Params["WA_UploadResult1_1"] = array(
'UploadFolder' => "../imagesupload/",
'FileName' => "[FileName]",
'DefaultFileName' => "",
'ResizeType' => "1",
'ResizeWidth' => "400",
'ResizeHeight' => "400",
'ResizeFillColor' => "#FFFFFF" );
// WA_UploadResult1_1 End
// WA_UploadResult1 Params End?>
<?php
// WA_UploadResult2 Params Start
$WA_UploadResult2_Params = array();
// WA_UploadResult2_1 Start
$WA_UploadResult2_Params["WA_UploadResult2_1"] = array(
'UploadFolder' => "../imagesupload/",
'FileName' => "[FileName]",
'DefaultFileName' => "",
'ResizeType' => "1",
'ResizeWidth' => "200",
'ResizeHeight' => "200",
'ResizeFillColor' => "#FFFFFF" );
// WA_UploadResult2_1 End
// WA_UploadResult2 Params End
?>
You can change the ResizeWidth and ResizeHeight to something that you want. You would want to make the same changes on the Products_Update.php page as well.
As for adding a 3rd upload, you would be able to do it, but you would have to make a good amount of modifications. If you would like to add additional images to the PowerStore, the easiest way would be to use PowerGallery, which has a gallery style made specifically for PowerStore. You would insert the gallery into the description.