Sorry for my late reply. I was using my W53 in windy and choppy conditions lately and the general conclusion is that she better excels in flattish water with max 10-20 cm chop. As soon as the chop worsens (30-40cm), control gets more hairy and speed does not increase dramatically with stronger winds.
1) iSonic W53 speed, 30 cm Drake slalom Pro fin, mast-track set at 50%, all straps back, Severne Code Red 7.7 m2. Offshore wind 12-18 knots with 10-20 cm chop. Vmax 32 knots.
2) iSonic W53 speed, 30 cm Drake slalom Pro fin, mast-track set at 30%, all straps back, NP RS1 6.6 m2. Onshore wind 18-23 knots with 30-40 cm chop and 50 cm swell. Vmax 28 knots. Lots of tailwalking because the fin was too big in gusts.
3) iSonic W53 speed, 26 cm Deboichet speed slalom fin, mast-track set at 30%, all straps back, NP RS1 6.6 m2. Onshore wind 18-23 knots with 30-40 cm chop and 50 cm swell. Vmax 29.9 knots. No tailwalking; board was kept flat in gusts and keep accelerating further and further.
As soon as I reach a wind lull, speed decreased dramatically as compared with a full-on slalom high wind board during match races, and this is becoming more and more noticeable when chop worsens. Jibes and pointing upwind are better with a full-on slalom high wind board when chop worsens.
Can you use your 6.9 m2 sail? Yes.
Can it go upwind? Yes when fully lit, even with small fins. Not very well in marginal wind or under-powered up.
Can you use it in 0.5-1m waves/swell and small chop? Yes, yes, yes down the lines! Hairy when going upwind against the waves: kind of a rodeo ride. B&J is definitely not recommended with such a light weight baby...