hi brad

: How much effort should be put into bevelling the forms?

none

I am using 18mm ply
: forms. Should I mount them with the centre of the form exactly over the 1'
: marks on the stong back, or with the pattern face on the 1' marks and the
: rest of the form further towards the ends, to be bevelled off?

mount your forms with the pattern face on the marks and the form towards midships. no bevel is needed...normally. what are you building?
regards;
daren......