Yep, have tried it many times - it works, but not very good
Balancing is an act, as most has way too long waterline (straight edges), so you can not countersteer much to keep balance, but have to rely fully on the kite control - which can be very difficult in extremely light wind
But upwind is good, and low end amazing
The same goes for SUP's - can also be ridden in extremely low wind, but they are too slow and too much rocker/soft edges for good upwind, but low end also good.
Both types are NOT very fun to ride IMO, except for the fact it is difficult and just the joy of doing it can be fun
Any really good lightwind board will be much better as I see it, and a race board same flotatioin and WAY better both low end and upwind especially.
But a big door or huge fast fish board is also much better, so I would not use much energy on using a windsurfboard.
Only if some cant afford a lightwind board, and HAS a small windsurf board, you could try this - the smaller the better as it can turn and easy to balance.
Just remove the footstraps (you stand much further forward than with a windsurf rig) and use a tad smaller fin as Higa says, and go
Kindly, Peter Frank