One point: you have to set NumberFormat property BEFORE loading the value into the cell. I had a nine digit number that still displayed as 9.14E+08 when the NumberFormat was set after the cell was loaded. Setting the property before loading the value made the number appear as I wanted, as straight text.
OR:
Could you try an autofit first:
Excel_Obj.Columns("A:V").EntireColumn.AutoFit