In the past, when fitter, I had a lot of casual fun working real HF DX with simple rig mounted antennas and batteries. In fact I have worked some impressive DX with QRP SSB using just the whip on the rig, mainly on 15m and 10m SSB. Best DX includes South America from my late mother’s back garden on 15m SSB with the FT817 at 2.5W setting
One advantage is you can move the rig and antenna of optimum signal on receive. A small counterpoise wire is pretty essential to get best results. When fit again I’d like to do more of this, but currently my poor health is getting in the way.
Others, far more dedicated than me, have worked far better DX. Some get up early to work Australia from beaches with QRP on 20m. I have also worked a long way into Europe on 2m FM with QRP. 6m SSB Es is certainly workable with small rig mounted antennas.
I think you have to believe than this is possible (HF DX) and it will happen. Think how strong some signals are. On the higher HF bands a base loaded, or better still a centre loaded, whip is not that far down on a full sized vertical.