I've e-mailed it to 7invensun, guess I'll also share it here
There is a small error in Unity version of SRanipal SDK, version 1.0.0.0, probably caused by copy-pasting error.
File: ViveSR\Scripts\SRanipal_Eye.cs, line 366
Function:
SRanipal_Eye.Focus(GazeIndex index, out Ray ray, out FocusInfo focusInfo, float maxDistance)
Description: maxDistance parameter is ignored in later call
Solution: Change line
return Focus(index, out ray, out focusInfo, 0, float.MaxValue);
to
return Focus(index, out ray, out focusInfo, 0, maxDistance);