I hadn't seen the bit about loosening the head a bit to achieve more aggression.
I loosened it a bit and it does seem to do that.
I haven't tried it as it is then quite free to flex and I don't like that.
Looking again at this it seems it is the same issue on both sides but on one side of the blade. The blade is snug on both sides in the same place and there is a very slight gap on the other part of the blade (because it is a slant - on the opposite sides). On the snug part there is no play in the blade and the other side there is very slight play - I can get a blade in there and the blade can be moved but only very slightly. This is happening on both sides. A shim to make the blade more solid might actually help based on that video above. I can get a photo if you want as this explanation might not be 100%- need to get out right now as it is carnival here in our town. Let me know and I can get an image on - we might have the same issue here.
I can get a blade in at all four corners happily.
Probably about a third of the way in.
The middle third, however, is tight (where it screws in).
I never did hear any more from the vendor actually.
RE the shim, I am just removing the sharp bit of an old blade aren't i?
I put the shim in and it still has similar fex in the blade to without the shim.
(I would prefer less flex all over really, but, hey)
Having said that, I rather like it with the shim.
Seems a lot smoother.
I shall have to try with and without on the same day or something.
Thanks for that.