I got mine off, too. I tried to disassemble the freewheel as recommended above, but my pin wrench (an old VAR one) wouldn't reach them (they're pretty far recessed into the freewheel).
Did you remove the outer cog (or two) before you tried the pin tool? The Regina freewheel body was originally designed for a 4-cog cluster, so it is quite narrow. As five, six and even seven cogs became common, the face became quite recessed below the level of the cogs.