When on the ground you can just lean forward, then press the button you've assigned to re-center the VR view. Having leaned forward first moves you wayyyy back in the seat so you can reach those buttons for ground-start easily.
Once ready to roll, sit normal in your seat and re-center the VR view once more.
That's how I do it and it works well enough.
Another pointer - be sure to press Alt+Enter after DCS starts for it to run in full screen, else you might find yourself clicking outside DCS while trying to reach those aforementioned cockpit switches during startup. :)