FCP performance with Vega 64

Hi guys, I'm running a Vega 64 LC. If anyone here is using a Vega card and happens to use FCP, could you share you BruceX results? It seems like my card is not being completely used since my BruceX took around 33-40 seconds. Besides, FCP performance is very poor during editing, making it almost mandatory to use proxy, which I thought should not be the case with this card. The thing is that I get around 22k in LuxMark, so the GPU is recognised by the OS, the problem seems to be with FCP. I'm running High Sierra, tried with beta software but same performance :(