Another leak down test question

[griffbones]

Just like in another recent post, I too found the $17 leak down tester thread and made myself a test kit.
My questions are:
1. What position should the piston be in to properly perform this test? TDC?
2. If pressurized to 5 or 6 PSIG, how much leak down in a 15 minute time frame is acceptable?

Thanks in advance.

 

[griffbones]

Does anyone have experience with this topic?