Again, thank you all so much for your posts. Each one has added interesting / important information !
Plumb Bob, I am in the process of converting my ICAO GPL license to an EASA SPL. I might consider adding TMG to it someday in the future, but there's only one TMG in Portugal ( HOFFMANN H36 DIMONA Mk.II :CS-ASJ )
Yes, each glider I have flown has it's own sideslip / fwd slip behaviour, and rudder / aileron authorities !