At the beginning of the sporadic E season I built a simple ground plane for 4 and 4m, just using a 6m fibre glass telescopic fishing pole and a bit of wire. The antenna works fairly well on 6 and less well on 4m, mostly due to its low height - the top of the antenna for 4m is only slightly over 5m above ground, so shaded by houses and trees.
The pole influenced the antenna considerably, and I was very happy to have my antenna analyzer when cutting it to the bands.
This antenna has worked about 40 countries on 6m, and 5 on 4m.
On 6m it operates a bit better than the R6000 at 3m height.
It was time for a better 4m antenna for local (FM) and a minimum amount of DX, mostly sporadic E. I decided to use a Sirio CX4 which is an end fed half wave antenna. The 10m half wave came down and the CX4 was raised to about 6m (feed point for the half wave about 7m. As expected this works much better than the low ground plane.
For working local stations in SSB, where most are running with horizontal antennas, I need to mount some kind of horizontal antenna myself. I am considering initially to male two dipoles or delta loops for operation in different directions, just to get it running. More elaborate antennas will have to come later.
Now, what to do about 6m ? I want to raise the feed point of the R-6000 to about 7.5m, and that should put the 6m part of the antenna a bit further from the trees around it, giving a better 6m (and 10m) range. On 6m some horizontal antenna is needed, and, again, I consider starting with 2 dipoles or delta loop antennas. A simple "V" shaped horizontal dipole could provide some degree of omnidirectional radiation, though.
For an omnidirectional antenna a "Squalo" (square halo), or a "Big Wheel" could work, or two "double quad"elements at 90 deg. could be fed in 90 deg phase difference, providing a modest gain.
I would like to generate some more gain on 4 and 6, and some kind of phased arrays for fixed favourite directions are in my thoughts. Older hams may be familiar with the "Lazy H" antenna which has a bi-directional gain of about 6dBd. This antenna can be fed with open line feeder and a tuner, making the same antenna suitable for both the 4 and 6m bands. There are other options, and they will be explored.
For now the 4m antenna is operational, and I am often QRV on 70.450MHz FM, and sometimes around 70.200 SSB or CW.