This model shows how the high angle lobe becomes depressed when the flag is raised from 6 ' to 100' and 120'. Notice that the gain is down slightly, but much high angle noise will be suppressed (shaded blue).

This high angle suppression is at a maximum at 125', after which a higher angle lobe starts to develop.

This looks like it could be a very good rotatable RX antenna.  A three-quarter scaled version could be built easily rotatable to be placed on top of a TX tower and used with the appropriate pre-amps.  The tower MUST BE DE-TUNED since modeling shows that the pattern is destroyed when a resonant antenna is near-by.

Full size flag model (14' high by 29' long) 1.830Mhz.

The pattern for this antenna on 3.5 Mhz is very poor at 100' and 120' because of a very nasty high angle lobe.  Optimum height for a 3.5 Mhz Flag is 1/4 wavelength.....around 61'. see here 80m Model

It is possible that modeling using a NEC based program may show some different results since the 6' model is close to the earth. ( I expect the gain difference may not be as great since MININEC apparently does not account for earth losses when wires are close to the ground.)