The way the RadSpreadProcessing decides if a row should be exported works slow. It iterates through all the rows in the UsedCellRange and checks if some property is set and if not, checks if some cell is set. This is slow because each row is checked one by one.

If shape extent is declared, the two cell anchor points for the drawing element are ignored. For example if the TwoCellAnchorElement's from and two points declare that the image should be anchored starting from cell A1to F10 and further in the drawing declaration there is defined extents element with image size values, anchor element's points are ignored. 

For example, if a user wants to set a 5x5 array of values in the worksheet he has to iterate through all the values one by one and set it to the worksheet. With that API the user should be able to set the entire array with just one method call giving it the array.