Thanks for all the replies,
I did some more reading (Like 8 hours worth) and it seems the 75 mags would fit in the P09 but they need to be longer so I've 3D printed a new longer base plate (that still keeps the mag limit at 10) that from my reading should solve that issue. I also plan to ether widen up the base plate or make a internal sleeve to stop the wiggle I see people mention but that will be once I collect the pistol in a few days.
I also intend on making up a new mag release with a larger catch point if I find my mags drop out. - Lots of work but gotta keep it legal here
If anyone is at all interested in getting in of these base plates that should allow the use of 75 mags in the P09/P10F feel free to PM, Happy to supply the STL files once its out of testing.