I think you guys need to get a manufacturing consultant if you havn't already. Based on what I'm seeing I dont feel that you've done this or the consultation outcomes weren't realized. IMO Its critical to your business model that you use a deposit preorder system tied to a modifiable user account. besides the obvious reasons it could enable a buyer to give sell his preorder spot to the person that buys their pinball machine. You would reduce the amount of abandoned orders. Maybe not for your future version of the business where you move away from screen printing but certainly now. Paypal is not the be all end all way to recieve deposits. You could use square and shopify to create whatever structure you need.