How do you get the control lines to be the exact length???

Yeah that is the easiest way.  Myself I bought two bulk rolls of .015 from MBS Model Supply  aka Melvin  Schuette.   Make the ends on the roll.   Roll them out and cut over size to have material to work with.  Before cutting put a little stretch pull on the lines, then cut and finish the ends.  I usually get within a 1/4 inch.  I don't know how Tom Morris does it but I've only had one set come out exact.   That is the reason I have a line clip maker so I have line clips in 1/16th inch increments.   It takes patience and practice to get it right.   The reason I buy in bulk is I fly different events and a few different plane types other than stunt.

Make one line, both ends finished, Put one end on second line, hold the other end up in the air a few feet along side the first line, pull them to get a slight sag, align the second line exactly next to the first line, mark the end of the second line and then finish it. Should come out really close to same length. I do this on the sidewalk in front of my house. I stick a piece of music wire in the walk for the first ends and work freehand at the other end.

If you have an adjustable handle it doesn't matter...... You can make major or super- fine adjustments between flights at the field.  Of course I use a cable handle which makes it simple. 

Dave