@Wahaha360 I REALLY REALLY suggest you to support in the P1 also the HW Labs 240 Slim Radiator.
I am testing it now and is equal to my XE 60mm with fans till 1300rpm! It's incredible.
Of course if you keep the 280 rad support it will fit. (There will be space also for the GTS 280??)
I assume you are running Noctua Sterrox A12-25 on HWL GTS240?