hey
first sound like your 9 m kite have a wind range equal to 8 m (or even 7 m) kite..
for the wind range that you aimed : 16-28 k (72 kg) i think you better go with the 10 trigger (~14-30)
but if you already have 12 m kite & you want to hold your "small" kite up to 30+ k > go for the 9 trigger(~16-33) ,9+12 it's better combo !

Slappy,

The Caution Mayhem is from 2007/2008 or if it's a Mayhem X could be 2009 it so comparing it to the 2012 Trigger is really chalk and cheese.

Although I haven't flown the 2012 Trigger I have flown the 2011 and as a comparison the 9m Trigger will def get you going a lot quicker than the Mayhem, but as you have said, the Cautions are superbly stable in "overpowered conditions" and you can expect the 9m Trigger to get too much to handle a lot sooner than the Mayhem.

So, if you go for a 10m Trigger it would be like going up TWO sizes for you, and I'd suggets that the 9m Trigger is probably the right size option to consider.