I wasn't able to use a V block - I stuck with the vice idea.
I spent well over 2 hours re-adjusting the laser.
I've got it much better - it's usable now.
I labelled each of the 3 adjusting screws so I could keep track of what I was doing -
labeled A, B,C.
e.g the first iteration was undo A & B by 1/2 a turn and tighten C - then retest -
that improved it.
A & B undo 1/8th turn C tighten - made it better.
C undo 1/16th B&A tighten etc etc.
If the laser got worse I would undo what I'd just done and try another combination.
I also found I didn't need to clamp it up tight with the adaptor set screw each time -
I got a feeling for how the spot was moving in a circle when I turned the laser.
I went through 25 iterations till I got it right.
See the picture.
The error is less than 5mm at 4.3 meter target distance which
for my 1016 mm telescope will represent less than a 1.25mm error.
cheers
Allan