Hello i'm having a bit of a issue in trying to work out what would be best for me. I want a frontal partial system to cover my receeded hairline, I don't know if i should have two separate pieces to cover each temple or one whole one and shave my hair a little so it's straight beforehand ? I have a bad mature hairline so the middle of my hairline is quite forward

I don't think you'll really know until you try.
There are a few here that use 2 pieces but I've read at least a couple of times that people who used 2 pieces eventually have decided it was easier to just use 1 piece as the hairline then appeared more consistent.

I was thinking one might be easier to be honest ! lining up two might be tricky plus there might be blending in issues with the hair on my hairline already !

Tom

It might mean shaving some of your front hair off, but if the overall result looks better, then its worth it.