Chrisansilver,
With the K140 at high idle she starts moving forward without even opening the throttle. I take off at half throttle with the K140. Try a smaller turbine in it first. If you going to do the 3D jet thing then by all means or stick to the grass then you will be fine. It will be a rocket.
I am thinking of fitting a 16KG to do 3D, will keep you posted.
Enjoy and I wish you many happy flights with the Predator.
Have a great day
Regards
JB