The HF-1 underwater weight is 250g. My old Z240s (still going strong by the way) are 77g each underwater, for comparison.
That is a very very very big difference. My Z330 are just 20 grams negative. So I am afraid my set will sink now. I don't see the option to make it more upward lifting as I cannot change the floating arms for the macro strobe every time I change a strobe. Also this will not fit in the luggage when flying. Adding foamblocks will not help for me too, as I am diving too deep (don't take foam blocks over 60m, and if you have been to 100m you can throw them away, haha).
It was that I had to buy this Backscatter strobe as Inon still has no Z400, and the strobe itself looks ok, but it is soo negative. The new Retra is sadly also not on the market (april).
And another thing I really don't like is to sell it with a very blue diffuser and not with the more normal 5500 diffuser. So you need to buy another diffuser. This makes the total price of the strobe higher. And it is here around the same as the Retra Maxi. And the Retra Maxi has a RN of 46.
But for now I hope I can use the Backscatter HF for over 5 years, that it is more durable than Inon which I found really not durable (bad magnetknobs to turn it on). Inon Z330 only lasts 3 years which is very short (The S2000 lasts much longer, but is not powerfull).
As soon as I have my own real experiences with the strobe I will write them online. As I think the results will be ok (I will use it together with the Z330 that is left).
Next weekend I will not test it as I want to do macro photography, so use the macro flash.
They say that the aftersales from Backscatter is better than from Retra, but I hope I will never need after sales.