spinout on KODE 103, help !!!

[kid]

hi all

I am a french 1.75 m & 68kg windsurfer (quite "old" /52) and has been practicing for ... ouf 30 years

So I am quite experimented but not expert (see, lake, small waves)
After some 12 years with the same boards and sails (85l & 125l = 4 + 4.8 + 5.3 + 6 m²) i decided to change all for an unique KODE 103 (2010 good second hand opportunity, for me one for all wind and water) with North ice & Duke (4.5 + 5.2 + 5.9)

On the board I put the straps in front & external position (4 straps), and the drake standard fin (30 cm)
All my trails were for the moment ... unfortunately soo bad : spinout, spinout & spinout , what I never had with my old boards & sails. (only 4 days of trials, as I bought the board in summer)
The position of the mast foot was in the recommanded position or in Front (what is better but not ideal as Spinout continued)

Please could you give me some advices ? I am sûr I have to re-learn windsurf with this new board but what could I do as set up to facilitate my learning.

Position of straps ? front or back, 3 ou 4
perhap's new fin ? fin in what position front or back ?
I always navigate with wishbone quite below the shoulder / 6 to 10 cms (bad habit ?), is a possible problem ?

Thank you very much dear Starboard experts and sorry for my bad english.