Some people just need a fire lit under their asses.
That guy from canada I dealt with didn't think I'd do a chargeback but he got fucking caught with his pants down when they okay'd a 100% chargeback in 3 days, which was literally hours after he sent me a partial refund & missing parts. I eventually had to give it back, but kept the remaining parts & half my money. Then I got a cheap mani w/o crack and now I'm golden, just took 4 months. It was cool to effectively be paid to buy a junk GSR manifold... ;D
I'm a strong believer in a 10-20% downpayment, then the remainder when it's finished. That makes projects move pretty quick.
Thats the problem most guys in this field cant work that way. Most barely can make rent these days. I would never take a 10 percent discount to port a head/manifold/machine work. We dont work knowing on the 15th the same check is coming and can balance around that.
If you have a solid rep and do custom work you should get paid atleast half up front. This isnt doing a timing belt if you get a 10 percent deposit for a custom setup your basically deeper in supplies if the guy bails. You now have 10+ hours of work and your behind even more.
For people who dont making a living doing custom work that concept might seem like it works. For those involved its suicide.
Why does everyone think people who own a business have tons of money. Not to mention if you can keep your bills paid in this field your fuckin lucky let alone hunting people down to pay the rest of a bill.
Conclusion:50 percent down is fair and no refunds if they change their mind since some how someones Grandma just died,they got a dui etc like thats the guy doing the one off works fault.
I get shit out fast and if someone offered me 10 percent of the total bill I would tell them to go fuck a donkey.