table runner length?

Anyone know the best length to make a table runner? I plan on making
one for my mom for Christmas. The table is 42" round. I want to use
the 12" Oregon Trail block. Check here (scroll to bottom),

http://www.quilterscache.com/M_O/Ont...railBlock.html

Should I make 4 blocks and have it hang over the sides of the table
several inches, or should I make 3 blocks and add a little to make it
hang over just a couple inches? I'd like to add the tassles too. Is
there a rule of thumb about how many inches a table runner should hang
over a table edge?

Other quilting news, I am making good progress on a couple floor
pillows for xmas gifts to my sisters. They are both samplers, I'm using
flannels and they will be about 27-28 inches. I love flannel and these
pillows are turning out great. I just might have to make one for myself!