big10p - I tried a very similar one by the same manufacturer (an older version/style maybe?) and it wasn't that good TBH.
Looked like this one:
http://www.maplin.co.uk/module.aspx?ModuleNo=27476&doy=21m12
As you said, having the dial anything less than max didn't seem to work much at all.
Looked like this one:
http://www.maplin.co.uk/module.aspx?ModuleNo=27476&doy=21m12
As you said, having the dial anything less than max didn't seem to work much at all.