I am 5'11" but got extended because
1. I am using the stock seats and sliders (for now) and they are a comfy 4" thick,
2. It will leave more room for long legged people to drive my Goblin
3. I think it will help with weight balance, as the occupant's weight will be further forward, and
4. If I do put in race seats, I could have some room behind the seats.