Hi Shaz

I wouldn't expect really problems with air speed. I would expect problems with the turbine settings, because an altitude of 6300 feet (app. 1920 m) ANDa "flight level" of app. 1000 Feet (300 m) could disturbe the turbine. I would ask the manufacturer of the turbine if you have to adjust some settings for this altitude. Perhaps the fuel pump or something else.

A runway of 625 foot (200 m) should be long enough,... if you use the whole distance and/or your brakes are working well :-)

Kind regards
Rainer