2.5gbe max real speed

I have been pulling cable true my house, and got to test it quick yesterday.

The transfer is stable 280MB/s between 2 computer over 50 meters of cable true a switch. Im happy with it. More courious as 2.5gbe could theoretically do 300MB/s

The computers hardware can handle it, no doubt.

The cat6 cable is solid copper from good brand, so is the switch and nic.

But i used cheap rj45 connectors and a flat ethernet cable for 1 meter for testing.

Could i get the last 20MBs with those, or is this as good as it gets?