XInput: how do I access vibration on 360 controller?

I'm working on a fighting game, using two 360 controllers for 2 players. To get this to work, I've added xInputPureDotNet to my project. Works perfectly, only minor bug seems to be it detects controller 1 as 2 and vice versa, not a big problem to work around. So, In the sample unity project xInputTest which is included, there is a line accessing vibrate for each motor based on trigger input. Since I don't really fully understand how xinput works, I've been trying to use that example to add force feedback to my own project. The line for vibration is :

 Gamepad.SetVibration(playerIndex, state.Triggers.left,state.Triggers.right);

By exposing the state.Triggers.left,state.Triggers.right in the inspector, they appear as normal axis input, maxing out at 1.

However, if I plug in a 1 through code, such as :

var vib1 = 1; var vib2 = 1; Gamepad.SetVibration(playerIndex, vib1,vib2)

(the format is SetVibration(XInputDotNetPure.PlayerIndex,float,float))

Doesn't seem to matter what number I use, all I get is a faint murmur on one controller. The xinput test only seems to take input from one controller (controller 2), so what I want to figure out is:

A: how can I set up the xinputdotnetpure.PlayerIndex for each controller, since the example only seems to work for one? Note: the test detects both controllers, as evidenced in the debug log. Only seems to take input from one though. All I need is to be able to refer to each controller as a PlayerIndex.

B: since the two latter arguments are floats, can't I just set them manually? Why doesn't this work? In the test scene, (using the state.Trigger.right etc.) the vibrate fully works, at least on the one controller. But if I replace with my own floats, just a faint murmur.

If there's anyone out there who knows how to do this, an example would be extremely helpful.. Thanks in advance for any ideas!

Update:figured out the PlayerIndex, it's PlayerIndex.One, PlayerIndex.Two, etc. so now I've got the vibrate basically working, just not as strong as I'd like it to be. Here's the script I'm using, in case anyone's interested:

 using UnityEngine;
 using XInputDotNetPure; 
 
 public class XInputVibrateTest : MonoBehaviour
 {
     public float testA;
     public float testB;
     public float testC;
     public float testD;
 
     void Update()
     {        
         GamePad.SetVibration(PlayerIndex.Two,testA,testB);
         GamePad.SetVibration(PlayerIndex.One,testC, testD);    
     }    
 }

then I just set the floats when I want vibration (again, doesn't seem to matter much WHAT I set them to, that's the issue now.. I think it goes 0 to 1, but I can't get the full vibration as in the demo project no matter what I try.)