For Dvorak with a little assist from unix

First row

$ awk '/^[,.pyfgcrl]$/ { print length(), $0 }' /usr/share/dict/words | sort -nr | head

3 pry / ply / fry / cry

Second row

$ awk '/^[aoeuidhtns]$/ { print length(), $0 }' /usr/share/dict/words | sort -nr | head

15 tendentiousness

14 assassinations

13 instantaneous

13 insidiousness

Third row

$ awk '/^[;qjkxbmwvz]*$/ { print length(), $0 }' /usr/share/dict/words | sort -nr | head

4 xxxv

3 xxx

3 xxv

2 xx