I’ve been experimenting with 5W from the FT450D these past couple of days – only FT8 so can’t really claim it to be QRP… and it’s working well with spots and contacts all over Europe, and spots up and down the east coast of the US and into Canada. This was all on 17m, so a compromise on my loft fan dipole which is (still!) only cut for 20 and 6.
Leaving the rig on 5W also has the advantage that it doesn’t matter if I forget to change the tx power when I switch in one of the transverters.
In fact, as an antenna the bit of wet string is pretty dire. Plans to put a wire outside remain on hold because we need to get the chimneys sorted due to leaks and naff pointing. Once that’s sorted it will be too miserable to work up there!