You can pay it out either way. If you send him an email and let him know you want to pay the other half early, he can send a PayPal invoice to you. That's what he's done for me. He's a really easy guy to work with.
Hey, I went with Toku Taku for my Hakaider Squad preorder and had a question I wondered if you could help me with (since I can't see an answer on the FAQ page). I went with the half-payment option but now do I have to pay the second half on release or is there any chance I can do it sometime beforehand (such as when I have the spare money to)? I can't see an option that says "pay other half" or anything like that.