holy 28m! You'd need a craine to launch it nearly lol! Your 16.5 should do you, depending on your weight, board size, and expertieze, get you out in 14-16/17 knots... If you need a larger kite, just go 20m so you don't have to sine it in 14 knots, just cruize instead etc. Or get a specific light wind kite like the Cabrinha contra and Slingy Machine (brought up in topic in teh gear review section and here) Ask a mate you kite with to have a go at another kite brand, because something that suits me, might not suit you etc; kites are very individual to the person...
2005 Cabrinha CO2 6.5m, 2005 Cabrinha Element 10m, Naish 12m and Naish 16m (02/03 models I think-ride like a charm

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2005 Cabrinha Labrat 140 Board
Goodwinds and happy kite searching

Elizabeth Bate - Wello Kiter