Hello all,
just to tell you all I've revamped my code now, and it works SO MUCH better using just "strings" vs. formerly "Strings".
The downside is, you must dig deeper into the bits, and ALWAYS be aware of the sizes of your arrays, and properly attaching a '\0' to the end manually in various cases.
And then, you must know in advance what sizes you would expect. Dynamic sizing is out of scope here.
One thing that I would want to ask from the regulars/Arduino Gurus here, would be to add a comprehensive chapter upon the "string" capabilities to the main Reference documentation. I know this is largely C/C++ stuff, and this is also how I got along by referring to various other sources on the net. But it would really help to ease things if you'd have a description for the "string" (char *) functions as well as for the "String" methods.
Just as well, I miss a description of the mathematical functions such as "exp" and "pow" and so on.
Really would like to see some reference to these.
Thank you all for your effort - you made my day, and saved my week 
Kind regards
stargar