As an addon to my question, I have another one.
Say you have an .rdlc file and you want to make changes to it, apart from formatting changes which I have already done.
Can you add fields, etc. without having to go back to the.rdl file, changing it there and having to convert the updated rdl to rdlc all over???
My answer is just based on my experience, I find in SSRS development anything that changes the amount of data to be displayed it is quicker to clone the existing report because when I make changes even in BIDs I get strange errors, create a clone everything work as expected. This is assuming your new data comes back on the data pane.
Kind regards,
Gift Peddie