Your bandwidth is correct for a 20 meter ground plane. At 14 MHz,
covering the entire band is not a problem.

To drop the resonant frequency down to what you want, you have three
choices:

1. Add length to the vertical section.

2. Add length to all the radials equally.

3. Insert a small coil in series with the base of the vertical
section. Start with about one turn, one inch in diameter.

Since you say this thing is hard to get up and down, I would recommend
either 2 or 3. Either one will do, but my personal preference is for
the coil *IF* you can insert it in series easily. If not, go for the
radials.

It's good that you have the SWR analyzer. It will save a lot of hair
pulling.

GL!

73, Bill W6WRT