i known some of the carpenter collecting 40% deposit upfront, and "promise"
follow my drawing, end up Owner call me said their work are very bad, some size are totally wrong, very upset and fed-up

but, paid up 40% already, what to do?

i would suggest 20% for deposit, 7 days of work would be another 20%, it would be fair to owner and designer/ contractor company

but true~ If RM10k, deposit RM5k is reasonable (base on how reliable of the company)