I tried using Rinkya once and they were a bunch of dickfeelers in e-mail. I was basically just asking about their combined shipping and warned them that I was buying something huge and would like to have some little things thrown in the box too, instead of doing some idiotic shipping.
They acted bothered by it, gave me a hassle, and said if I was that worried about saving $$, I should use boat-mail.
So I said f*ck you guys and used Celga. They did what I asked without a single question.