I am 11 stone, 6ft tall and use a 153!
It is the perfect board for me in all conditions, including powder, but it is a true twin-tip.
If you can, try it before you go - good advice from above!
If there will be new powder, then yes, lean onto your back foot to lift the nose of the board. Also, keeping the kite high, to give you some lift, will help.
I have been surfing, kite surfing and snowboarding for some time, before doing snowkiting.