Minecraft Server in systemd

[Unit]
Description=Minecraft Server - %i
After=network.target

[Service]
WorkingDirectory=/opt/mcserver/instances/%i

User=mcserver
Group=mcserver

Restart=on-abnormal
GuessMainPID=yes

ExecStart=/usr/bin/screen -DmS mc-%i /usr/bin/java -Xms7G -Xmx7G -XX:+UseG1GC -XX:+UnlockExperimentalVMOptions -XX:MaxGCPauseMillis=100 -XX:+DisableExplicitGC -XX:TargetSurvivorRatio=90 -XX:G1NewSizePercent=50 -XX:G1MaxNewSizePercent=80 -XX:G1MixedGCLiveThresholdPercent=35 -XX:+AlwaysPreTouch -XX:+ParallelRefProcEnabled -jar minecraft_server.jar nogui

ExecStop=/usr/bin/screen -p 0 -S mc-%i -X stuff "say Shutting down in 10s...\015save-all\015"
ExecStop=/bin/sleep 5
ExecStop=/usr/bin/screen -p 0 -S mc-%i -X stuff "say Shutting down in 5s...\015"
ExecStop=/bin/sleep 5
ExecStop=/usr/bin/screen -p 0 -S mc-%i -X stuff ^C
ExecStop=/bin/tail --pid $MAINPID -f /dev/null

[Install]
WantedBy=multi-user.target