same pump as me then, all works fine for me with 60 meters although never used 8mm so maybe my flow is reduced in comparison, I do have an eco flow controller but its usually on full most of the time
somone did expain a few days ago (wally I think) the physics behind using a smaller bore will not create more pressure but reduce flow rate, something to do with creating "back pressure"
has now got me thinking that I maybe better off using 8mm at 100 meters, then I can use my pump controller more to adjust flow. I had been in two minds as to what to buy because I need to conserve water and make it last as long as I can, not because of the size of my tank (650) but because of parking issues and refilling at home.