Hi Bob,
I don't think that all Star yachts post 1945 had squared off sterns but believe that the change was made much later than this, certainly in the late 1970's catalogues the stern was still shown as rounded but this might be due to a reluctance to spend money on re-photographing the range… I suspect that your yacht probably dates to the 1960's.
Your painted deck is quite usual, most SY/6's are finished in this way as they were "The senior models of the Popular Series, these boats represent the ultimate in solid hulled sailing yachts". (taken from a 1970's catalogue).
The varnished decks were primarily only for the "De-luxe, hollow versions of the Popular Series" – The MK/1, MK/2, MK/3, MK/4 and above.
The Vintage Pond Yachts site is mine but sadly I just don't have the time currently to add more information to it nor to make up any more Star Yacht stands. I will certainly be doing this at some point but I'm not sure when.
I have just checked and although I don't have any blue stands left I do have one available in green if you're interested? It's the medium sized stand that you'll need for a Southern Star.
Unfortunately the "Southern Star" transfers are no longer available.
I'm sorry that I can't be more helpful but I hope you have fun sailing her at Llandudno this summer.
Mark