Pat,

It is hard to give more than just very general guidance because "it depends".
The impedance of the antenna on the fundamental frequency and multi-band
frequencies of use will be the main determining factors. Frequently a 4:1
balun is appropriate for multiband installations since the impedence will vary
quite widely. It will be a good match on some and poor on others.

Personally, I prefer to use open wire or ladder line for multiband antennas. A
link coupled or double balanced tuner in the shack does the impedence
transformation with little loss.

73s,

Evan