Not with CF tubes but Alibaba for some electronic bits and pieces recently and had no problems. You can buy from multiple suppliers in the one order.
Turns out they don't pay the supplier until you receive the goods and then notify Alibaba that they have arrived. If you don't bother notifying them re the arrival they pay out after a set time, I think about the thirty day mark.
They also run a good conflict resolving service just in case of issues.
I would be happy to deal with them again.