it is also most likely dangerously too small for most of your waaaaaay too many lenses.
you are doing a full frame camera. depending on the lenses you use there will be moderate to severe vignetting at various wide angles. even the Z holder is only good down to about 20mm no matter which way you turn it.
just discovered? the cokin system has been out over 25 years now. i used the P series on my OM system way back and went on to the Nikon from there where i started to find the limitations of even the P mount on W/A lenses
the Lee holder and there associated W/A adapter rings (SWA) can reach down to 16mm on the Canon and Nikon FF bodies with very minor corner vignetting.
depending on the lens you are using the Lee and or the Cokin Z holders can add and subtract slots. giving a better FOV. the P holder has 2 models. the standard has more filter slots vs the W/A model with less. the real difference begins with the Lee's adapter rings. they are designed to position the filter assy closer to the front element then the Cokin or any other holder similiarly designed. the cokin has no answer to this rather innovative methodology. the few mm it does give you is really nice to have if you are running the real wide on a full frame camera
lenses on a FF body that benefit from the Lee setup
16-35/2.8 Lee though it requires a 82mm adapter
17-40/4 Lee works beautiful.
24-105/4 either Lee/Cokin Z works
70-200/2.8 either Lee/Cokin Z beautifully
any number of appropriately wide primes.
if you were running cropped (which you're not) it would be no issue but you you are really are thinking the P you will be at or over its limits already. it will be a dead end.
