Update ...
Finally got proper stands (open-style, wood, 18" tall, very similar to TonTrager) for the SHL5+, and what a difference they have made. The problem with excess bass that I described earlier is completely, 100% resolved. I have removed the REL subwoofer for the time being and still the bass from the speakers is astounding. You can actually feel the bass in your chest, something the SF Olympica IIs never achieved.
The other big surprise is the super tweeter. I guess it had to be raised further up the floor to really come into its own. The sound I’m getting now is airy, open, and extended. The soundstage has also improved both in terms of width and depth. One thing I appreciate is that the super tweeter only springs into action when called upon, otherwise it sits in the back and does not affect the music in a negative (bright, harsh) way. Well done, Harbeth!
Next weekend, I will do a side-by-side comparison between the SHL5+ and M30.1 and report back. But right now, I have to admit that the SHL5+ is proving to be a more engaging and versatile speaker compared to the M30.1. It is also, without a doubt, better than SF Olympica II in every regard.