I am currently wiring up a single-page checkout, starting with the walkthrough here (http://merchello.com/documentation/getting-started/how-to/Simple-Checkout-Process) and here (http://merchello.com/documentation/api/basket/orderprep).  I also had to piece together additional documentation to get the Stripe payment gateway, and shippable items (using a simple US flat-rate and Everywhere Else flat-rate) working.  So far, it works.. somewhat.  The issues I am running into with the code below are:

• Even though my country code is "US", the system returns the "Everywhere Else" shipping method when I call `shipment.ShipmentRateQuotes(false)`
• If credit card payment fails (i.e. invalid CC#), I still see an invoice generated in the dashboard.
• If credit card payment fails, each successive failure adds the shipping amount again, resulting in a wrong subtotal.  If the original subtotal is $15 with $5 shipping, the first invoice shows total $20, the 2nd invoice shows total $25, third $30, and so on.  Even stranger, opening the invoice only shows the $15 worth of items and $5 shipping total, with a $30 balance due?

Any help will be greatly appreciated.  Obviously, this is rough and will be cleaned up once I get it all working, so I apologize if it's hard to read.  I'm hoping something obvious is out of place:

        [HttpPost]
        public ActionResult Checkout(CheckoutViewModel model)
        {
            // STEP 1:  Save Billing/Shipping Address
            var preparation = base.Cart.SalePreparation();
            var billaddress = model.BillingAddress.ToAddress();
            preparation.SaveBillToAddress(billaddress);
            var shipaddress = model.ShippingAddress.ToAddress();
            preparation.SaveShipToAddress(shipaddress);

            // STEP 2:  Package into shipments
            var shipments = base.Cart.PackageBasket(shipaddress);

            // STEP 3:  Shipping Method
            foreach (var shipment in shipments)
            {
                var quotes = shipment.ShipmentRateQuotes(false);
                preparation.SaveShipmentRateQuote(quotes.FirstOrDefault());
            }

            // STEP 4:  Payment
            // has error occurred
            bool error = false;
            // do we raise events
            bool raiseEvents = false;
            // payment attempt result information
            IPaymentResult attempt = null;
            // get payment method
            var paymentMethod = Payment.GetPaymentGatewayMethodByKey(model.PaymentMethodKey).PaymentMethod;
            
            // get customer, items
            // Save the payment method selection
            preparation.SavePaymentMethod(paymentMethod);
            // make sure there is a billing address - it can be empty - it just has to exist
            if (!preparation.IsReadyToInvoice()) return Redirect("/cart");

            var args = new ProcessorArgumentCollection();
            args.Add("cardholderName", preparation.GetBillToAddress().Name);
            args.Add("cardNumber", model.CreditCardNumber);
            args.Add("expireMonth", model.ExpirationMonth);
            args.Add("expireYear", model.ExpirationYear);
            args.Add("cardCode", model.Cvv);
            attempt = preparation.AuthorizePayment(paymentMethod.Key, args);

            // if payment isn't successful, grab some information
            if (!attempt.Payment.Success)
            {
                error = true;
                // TBD - Not in Merchello yet
                // Notification.Trigger("OrderConfirmationFailure", attempt, new[] { preparation.GetBillToAddress().Email });
                _log.CreateAuditLogWithKey("Checkout failed - attempt payment failure", preparation.Customer.ExtendedData);
                return CurrentUmbracoPage();
            }

            // STEP 5:  Create the invoice
            preparation.PrepareInvoice();
            // trigger the order notification confirmation
            Notification.Trigger("OrderConfirmation", attempt, new[] { preparation.GetBillToAddress().Email });
            
            return Redirect("/receipt");
        }