the 12.5 is a/can be your anti-skunk tool. Very stable, decent amount of depower with a great combo of forward and lateral grunt via bar and kite position. 5mph will get you going on grass on the low end........ top end may be a but limited but Id say 13 to 15 is doable but you will require a sturdy set. This is a very powerful kite and will get you out and going (land or water;-)) on the lightest of wind days. I attached a small vid from the fairgrounds which is an inland spot with pronounced wind shadows and obsticles but the M3 flew rock solid..........enjoy!

http://vimeo.com/18323978