I think i have told you already in the other thread the concept of PPs and PP size.
The value is freely selectable upon creation of the VOLUME GROUP, not the LUN. However it limits your disk size as well as the total capacity of the Volume Group you create: maximum 1019 PPs per PV (=hdisk device) and maximum 32 PVs per VG.
Since you plan to create only one PV (as you said in the other thread) you should select the PP size so that you are not near the 1019 PPs per PV limit.
Example: If the LUN is, say, 50GB in size you should use a PP size of 256MB or 512MB if no other aspects apply.
This way you will be able to use LUNs of up to roughly 250 (500) GB in size giving you a theoretical total of approx. 8 (16) TB in the VG. This should be enough space to grow into for most practical purposes when right now your VGs data fit into the 50 GB i based my example on.