Options and Recommendations
"That won't work" is the worst thing you can say to the client when they suggest an approach or solution to something.
No one likes being told no, especially clients, and especially by their contractors.
Instead of saying "that won't work," you should
1) Acknowledge their approach as one way to do that,
2) Suggest two or three alternate approaches along with your reasoning, and
3) Recommend one of them and say why
This feels less "hostile" and gives the client control.
This goes against a lot of people's nature, especially technical people, who tend to be logically argumentative.
But when you're a 1099, you are mostly in the service business, the relationship matters a lot, often more than technical correctness.
Want the full playbook? Check out Going 1099.