The way you address your email to Koji can influence whether you get a reply or not. As has been mentioned, if there's any hint in your email that you're hem hawing, Koji's not likely to reply. It's happened to me before the first time I contacted him about Staxs. Emailed the first time to ask about the price, and got a reply within hours. Emailed back saying I wasn't ready, but that I had questions regarding the customs fee. Never got a reply.
The second time around, I asked for the price, and told him I was ready to buy for sure. The emails flew back and forth smooth as butter, especially during the period when I was wiring the money over to him. I bombarded him with emails to check if my money made it across and double check his bank account info, and got emails back within the hour.
BTW, regarding customs...if you are a serious buyer for something as big and expensive as the Omega IIs, he can mark them as a gift. He did for me at my request. It boils down to whether you want them insured or not basically. For something like the 303/404s, maybe not.