Dan,

If you want to design a shortened dipole with loading coils you should
download the freeware package HamCalc. It is a large collection of
BASIC programs which run in a DOS window. The package can be
downloaded from http://www.cq-amateur-radio.com/HamCalcem.html

There are several programs that deal with shortened, centre and
off-centre dipoles. Loading coil design using standard forms such as
PVC pipe is included.

Regards - Roger