RFM has nothing in the limitations section. 407 does but not the 206 series. The limitation on the 407 and other rigid rotor systems has to do with mast stress and lifetime of components (like the Vne on an S 76), not any physical limitation.
I agree with Sousa: way back in your initial license training for all pilots is the sloping ground exercise. You work at steeper and steeper slopes until you run out of cyclic (either left or right , fore or aft) before you get both skids on the ground. Assuming you haven't got mast bumping yet, that is your limit - you don't have to look it up.
Treat every landing like a slope landing - slow. And don't commit until you get both skids on - good technique and you won't get into trouble in the rest of your career.
charon