Propagating Glandora prostrata

When I started my garden, back in 2021, I found and added Glandora prostrata ‘Heavenly Blue’ (AKA Lithospermum Heavenly Blue; Lithodora diffusa Heavenly Blue) as a possible ground cover.
It settled in nicely so I got a couple of additional plants to augment it, but they definately were not happy. They apparently like acid to neutral soil. It appears that my soil which is neutral to acid, was not quite acid enough for the new plants.
I added ferrous sulphate and sulphur which helped but they still struggled.
So I have decided to propagate from the original plant, as it likes my soil.
On line, most sites reckon that they should be propagated from semi-hardwood cuttings, while others state that they have had zero success with s-hw but good with soft wood cuttings.
Question, gurus, one and all.
Have any of you had any experience with propagating this and what success or otherwise did you have?

 

Only time I have managed it was with newly formed shoots when they were still reddish in colour. No other cuttings rooted.

 

Yeah, softwood/new shoots. In damp sand. they root easily, but that's when I found out they didn't like my chalky soil!

 

Thanks guys. I'll start harvesting soon, then.
Bottom heat any advantage?

 

I didn't use bottom heat...in fact, I don't with a lot of my softwood propagation now.