We can place a directional rose anywhere on the map via -T, and most easily via justification codes for the 12 points on the map. However, if labels are requested then two issues are apparent:

1. The default font used need to scale with the symbol and not be a fixed separate setting. Turns out this is FONT_TITLE which defaults to 24p,Helvetica,black. This is way too big for all but poster-size maps I think, so I am sure any users of -T also sets a smaller font that is suitable. In fact, our own example in the cookbook (GMT_obl_merc.sh) uses --FONT_TITLE=8p.
2. The space needed for the labels needs to be considered in the justification so they are not falling outside the map

Here is the what is happening now:

At least in modern mode that font should scale with the rose symbol size. For both classic and modern the offset should take into account the labels.