Hi Sander,
You can buy HDMI extender cables, such as [https://www.walmart.com/ip/Ultra-Clarity-HDMI-Extender-Male-Female-Extension-Cable-15-Feet-High-Speed-2-0b-4k-Resolution-Ready-Supports-18gbps-2160p-4k-monitor-3D-Television-Xb/122832309?wmlspartner=wlpa&selectedSellerId=3021&adid=22222222227049909342&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=145305057963&wl4=pla-262108160868&wl5=1014232&wl6=&wl7=&wl8=&wl9=pla&wl10=113148584&wl11=online&wl12=122832309&wl13=&veh=sem|this] one. That way you don't need to cut or modify the Chromecast, risking damaging it.
- Jasen