PPLNS uncertainty. Please clarify (XMR pool)

Hello,

First of all @Poolmining Support, i want to say that i really appreciate all the hard work, the fact you chose to create your own pool and SW and the fact that you try to respond personally to as much of the questions possible. I feel like you are up to creating a nice loyal communuty here. Keep up the good work.

I am new to mining. Currently i am mining on the Monero pool.

Now to my PPLNS uncertainties. First i will state what and how i understand PPLNS works (please correct me if i got anything wrong) and then i will have some questions that i would like to get clarified.

What i know so far (hopefully correct):

PPLNS = Pay Per Last N Shares

-so when a block is found it pays for the last N shares submitted (and also takes into account the difficulty of those shares)

- N shares window is calculated as being X * difficulty

- share count is not resetted when a block is found

My questions:

1. What is the value of X in calculating the number of shares to reward? Is it according to FAQ (ie. value of 2?), or that is just an generic explanation?

2. What is the value of difficulty taken into consideration. Difficulty of the block that was found, or the difficulty that the pool assigned to the miner by VarDiff at the moment the block was found?

And a concern:

If the case is that X = 2 and difficulty = difficulty that the pool assigned to the miner by VarDiff at the moment the block was found, considering a pool that has a hard time finding any blocks, the Monero pool for example, won't this mean that miners are loosing shares that will never get rewarded?

To be more specific: I mine at an avg. rate of 475 H/s on port 3033 now. The pool dinamically assigs me an average difficulty of around 6500-7000. Let's supose 7000. And my total number of shares is 22402 right now.

If a block were to be found now, if the case is as stated above, then N = 2 * 7000 = 14000.

So theoretically i will be rewarded for the last 14000 shares and 22402 - 14000 = 8402 shares are lost. Am i right?

If yes, is there any way this can be prevented, like allowing miners to ask for a certain difficulty and prevent VarDiff? Or increase value of X?

I mean 8402 shares lost is...kind of a big waste, about a day worth of mining and electricity in vain.

I am eagerly awaiting your answers.

Thank you!