xkbsymbols for Group2, added uses for FKxx ?

[aunt_tilly]

I have a Windows program to convert to Linux. The program
will have to run on both platforms. On Windows, the program
uses ALT-Fn and CTRL-Fn (n=1 to 6) for various functions. On Linux, X and KDE use these keys. I would like to make
RWIN-Fn and LWIN-Fn (or xWIN+SHIFT) substitute for the Windows functions, but I can't seem to get all the pieces
correct. I have new xkb/symbols files including definitions like these:

partial hidden alphanumeric_keys modifier_keys
xkb_symbols "funkeys" {

// Begin "Function" section
key <FK01> {
type="FOUR_LEVEL",
symbols[Group1]= [ F1, XF86_Switch_VT_1 ],
[ F21, F31 ]
};
:
:
and this:
modifier_map Mod3 { <LWIN>, <RWIN> };

but I am missing something critical and I don't know what.

Thanks for any assistance.

A_T