The shopping cart and checkout functions on our web site are actually Paypal functions that we link to. When paying with Paypal, be sure you have your correct address defined in your Paypal account BEFORE you place your order and "check out" on our site, as the zip code you enter while viewing your cart contents is just for a shipping estimate ONLY, as the system does NOT know who you are until AFTER you log into Paypal account further into the "check out" process.
So, the proper procedure to make sure we get your current shipping address would be as follows:
1) Log into your Paypal account
2) Click on "Profile"
3) Click on "Add or Edit Street Address" and update accordingly
4) Log off of Paypal
5) Go to www.model-engine-plans.com
6) Place your items in the cart
7) Check out when you are done with your order - your "updated" address will be used.