So you're saying I cannot concatenate or use Flash strings using String class .. I'll guess I can just do it for my own private and modified version of String class.I think you're not being very helpful. See post above by Marek080 - that was very helpful and actually resolved my original problem.
Without the F() syntax, "hello" would be stored in your SRAM. But you don't have a lot of SRAM, so using the F() stores the string in the flash (program) memory, of which you have a lot. Projects that need a lot of strings will benefit from storing strings in flash, as it will free up ram for things like variables. But a flash string cannot be modified.baum